diff --git a/admin/src/graphql/updateHomeCommunity.js b/admin/src/graphql/updateHomeCommunity.js
index 19bfb7396..036db91e5 100644
--- a/admin/src/graphql/updateHomeCommunity.js
+++ b/admin/src/graphql/updateHomeCommunity.js
@@ -8,7 +8,7 @@ export const updateHomeCommunity = gql`
       location: $location
       hieroTopicId: $hieroTopicId
     ) {
-      id
+      uuid
     }
   }
 `
diff --git a/backend/src/auth/ADMIN_RIGHTS.ts b/backend/src/auth/ADMIN_RIGHTS.ts
index 9ba3e7ccd..69100d7d2 100644
--- a/backend/src/auth/ADMIN_RIGHTS.ts
+++ b/backend/src/auth/ADMIN_RIGHTS.ts
@@ -5,8 +5,6 @@ export const ADMIN_RIGHTS = [
   RIGHTS.DELETE_USER,
   RIGHTS.UNDELETE_USER,
   RIGHTS.COMMUNITY_UPDATE,
-  RIGHTS.COMMUNITY_BY_UUID,
-  RIGHTS.COMMUNITY_BY_IDENTIFIER,
-  RIGHTS.HOME_COMMUNITY,
+  RIGHTS.COMMUNITY_WITH_API_KEYS,
   RIGHTS.PROJECT_BRANDING_MUTATE,
 ]
diff --git a/backend/src/auth/DLT_CONNECTOR_RIGHTS.ts b/backend/src/auth/DLT_CONNECTOR_RIGHTS.ts
index 399b7c2d4..9b4c56eaa 100644
--- a/backend/src/auth/DLT_CONNECTOR_RIGHTS.ts
+++ b/backend/src/auth/DLT_CONNECTOR_RIGHTS.ts
@@ -1,3 +1,3 @@
 import { RIGHTS } from './RIGHTS'
 
-export const DLT_CONNECTOR_RIGHTS = [RIGHTS.COMMUNITY_BY_IDENTIFIER, RIGHTS.HOME_COMMUNITY]
+export const DLT_CONNECTOR_RIGHTS = [RIGHTS.COMMUNITIES, RIGHTS.COMMUNITY_UPDATE]
diff --git a/backend/src/auth/RIGHTS.ts b/backend/src/auth/RIGHTS.ts
index 012a4e627..d26bdc702 100644
--- a/backend/src/auth/RIGHTS.ts
+++ b/backend/src/auth/RIGHTS.ts
@@ -69,9 +69,7 @@ export enum RIGHTS {
   SET_USER_ROLE = 'SET_USER_ROLE',
   DELETE_USER = 'DELETE_USER',
   UNDELETE_USER = 'UNDELETE_USER',
-  COMMUNITY_BY_UUID = 'COMMUNITY_BY_UUID',
-  COMMUNITY_BY_IDENTIFIER = 'COMMUNITY_BY_IDENTIFIER',
-  HOME_COMMUNITY = 'HOME_COMMUNITY',
   COMMUNITY_UPDATE = 'COMMUNITY_UPDATE',
+  COMMUNITY_WITH_API_KEYS = 'COMMUNITY_WITH_API_KEYS',
   PROJECT_BRANDING_MUTATE = 'PROJECT_BRANDING_MUTATE',
 }
diff --git a/backend/src/graphql/arg/UserArgs.ts b/backend/src/graphql/arg/UserArgs.ts
index 406be14cb..681d3ce51 100644
--- a/backend/src/graphql/arg/UserArgs.ts
+++ b/backend/src/graphql/arg/UserArgs.ts
@@ -7,7 +7,7 @@ export class UserArgs {
   @IsString()
   identifier: string
 
-  @Field()
+  @Field({ nullable: true })
   @IsString()
-  communityIdentifier: string
+  communityIdentifier?: string 
 }
diff --git a/backend/src/graphql/model/AdminCommunityView.ts b/backend/src/graphql/model/AdminCommunityView.ts
index 50cee146a..8a685fa86 100644
--- a/backend/src/graphql/model/AdminCommunityView.ts
+++ b/backend/src/graphql/model/AdminCommunityView.ts
@@ -38,7 +38,6 @@ export class AdminCommunityView {
     this.updatedAt = dbCom.updatedAt
     this.uuid = dbCom.communityUuid
     this.authenticatedAt = dbCom.authenticatedAt
-    this.gmsApiKey = dbCom.gmsApiKey
     this.hieroTopicId = dbCom.hieroTopicId
     if (dbCom.location) {
       this.location = Point2Location(dbCom.location as Point)
diff --git a/backend/src/graphql/model/Community.ts b/backend/src/graphql/model/Community.ts
index 62cec9cf7..e5ccad59b 100644
--- a/backend/src/graphql/model/Community.ts
+++ b/backend/src/graphql/model/Community.ts
@@ -12,7 +12,6 @@ export class Community {
     this.creationDate = dbCom.creationDate
     this.uuid = dbCom.communityUuid
     this.authenticatedAt = dbCom.authenticatedAt
-    this.gmsApiKey = dbCom.gmsApiKey
     this.hieroTopicId = dbCom.hieroTopicId
   }
 
@@ -40,9 +39,6 @@ export class Community {
   @Field(() => Date, { nullable: true })
   authenticatedAt: Date | null
 
-  @Field(() => String, { nullable: true })
-  gmsApiKey: string | null
-
   @Field(() => String, { nullable: true })
   hieroTopicId: string | null
 }
diff --git a/backend/src/graphql/resolver/CommunityResolver.test.ts b/backend/src/graphql/resolver/CommunityResolver.test.ts
index c9c925a2e..5e7d929e2 100644
--- a/backend/src/graphql/resolver/CommunityResolver.test.ts
+++ b/backend/src/graphql/resolver/CommunityResolver.test.ts
@@ -1,5 +1,5 @@
 import { ApolloServerTestClient } from 'apollo-server-testing'
-import { Community as DbCommunity, FederatedCommunity as DbFederatedCommunity } from 'database'
+import { Community as DbCommunity, FederatedCommunity as DbFederatedCommunity, getHomeCommunity } from 'database'
 import { GraphQLError } from 'graphql/error/GraphQLError'
 import { DataSource } from 'typeorm'
 import { v4 as uuidv4 } from 'uuid'
@@ -10,19 +10,20 @@ import { i18n as localization } from '@test/testSetup'
 import { userFactory } from '@/seeds/factory/user'
 import { login, updateHomeCommunityQuery } from '@/seeds/graphql/mutations'
 import {
-  allCommunities,
-  communitiesQuery,
-  getCommunities,
+  allCommunities,  
   getCommunityByIdentifierQuery,
   getHomeCommunityQuery,
+  reachableCommunities,
 } from '@/seeds/graphql/queries'
 import { peterLustig } from '@/seeds/users/peter-lustig'
+import { createCommunity, createVerifiedFederatedCommunity } from 'database/src/seeds/community'
 
 import { getLogger } from 'config-schema/test/testSetup'
-import { getCommunityByUuid } from './util/communities'
+import { CONFIG } from '@/config'
 
 jest.mock('@/password/EncryptorUtils')
 
+CONFIG.FEDERATION_VALIDATE_COMMUNITY_TIMER = 1000
 
 // to do: We need a setup for the tests that closes the connection
 let mutate: ApolloServerTestClient['mutate']
@@ -46,11 +47,10 @@ beforeAll(async () => {
   mutate = testEnv.mutate
   query = testEnv.query
   con = testEnv.con
-  await DbFederatedCommunity.clear()
+  await cleanDB()
 })
 
 afterAll(async () => {
-  await cleanDB()
   await con.destroy()
 })
 
@@ -109,31 +109,38 @@ const ed25519KeyPairStaticHex = [
 ]
 
 describe('CommunityResolver', () => {
-  describe('getCommunities', () => {
+  describe('allCommunities for admin', () => {
     let homeCom1: DbFederatedCommunity
     let homeCom2: DbFederatedCommunity
     let homeCom3: DbFederatedCommunity
     let foreignCom1: DbFederatedCommunity
     let foreignCom2: DbFederatedCommunity
-    let foreignCom3: DbFederatedCommunity
+    let foreignCom3: DbFederatedCommunity    
+
+    beforeAll(async () => {
+      // create admin and login as admin
+      await userFactory(testEnv, peterLustig)      
+      await mutate({ mutation: login, variables: peterLoginData })
+    })
+
+    afterAll(async () => {
+      await cleanDB()
+    })
 
     describe('with empty list', () => {
       it('returns no community entry', async () => {
         // const result: Community[] = await query({ query: getCommunities })
         // expect(result.length).toEqual(0)
-        await expect(query({ query: getCommunities })).resolves.toMatchObject({
+        await expect(query({ query: allCommunities })).resolves.toMatchObject({
           data: {
-            getCommunities: [],
+            allCommunities: [],
           },
         })
       })
     })
 
-    describe('only home-communities entries', () => {
+    describe('only home-community entries (different apis)', () => {
       beforeEach(async () => {
-        await cleanDB()
-        jest.clearAllMocks()
-
         homeCom1 = DbFederatedCommunity.create()
         homeCom1.foreign = false
         homeCom1.publicKey = Buffer.from(ed25519KeyPairStaticHex[0].public, 'hex')
@@ -144,7 +151,7 @@ describe('CommunityResolver', () => {
 
         homeCom2 = DbFederatedCommunity.create()
         homeCom2.foreign = false
-        homeCom2.publicKey = Buffer.from(ed25519KeyPairStaticHex[1].public, 'hex')
+        homeCom2.publicKey = Buffer.from(ed25519KeyPairStaticHex[0].public, 'hex')
         homeCom2.apiVersion = '1_1'
         homeCom2.endPoint = 'http://localhost/api'
         homeCom2.createdAt = new Date()
@@ -152,170 +159,67 @@ describe('CommunityResolver', () => {
 
         homeCom3 = DbFederatedCommunity.create()
         homeCom3.foreign = false
-        homeCom3.publicKey = Buffer.from(ed25519KeyPairStaticHex[2].public, 'hex')
+        homeCom3.publicKey = Buffer.from(ed25519KeyPairStaticHex[0].public, 'hex')
         homeCom3.apiVersion = '2_0'
         homeCom3.endPoint = 'http://localhost/api'
         homeCom3.createdAt = new Date()
         await DbFederatedCommunity.insert(homeCom3)
       })
 
-      it('returns 3 home-community entries', async () => {
-        await expect(query({ query: getCommunities })).resolves.toMatchObject({
+      it('returns only home-community entries', async () => {
+        await expect(query({ query: allCommunities })).resolves.toMatchObject({
           data: {
-            getCommunities: [
+            allCommunities: [
               {
-                id: 3,
-                foreign: homeCom3.foreign,
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[2].public),
-                endPoint: expect.stringMatching('http://localhost/api/'),
-                apiVersion: '2_0',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: homeCom3.createdAt.toISOString(),
-                updatedAt: null,
-              },
-              {
-                id: 2,
-                foreign: homeCom2.foreign,
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[1].public),
-                endPoint: expect.stringMatching('http://localhost/api/'),
-                apiVersion: '1_1',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: homeCom2.createdAt.toISOString(),
-                updatedAt: null,
-              },
-              {
-                id: 1,
-                foreign: homeCom1.foreign,
+                foreign: false,
+                url: 'http://localhost',
                 publicKey: expect.stringMatching(ed25519KeyPairStaticHex[0].public),
-                endPoint: expect.stringMatching('http://localhost/api/'),
-                apiVersion: '1_0',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: homeCom1.createdAt.toISOString(),
+                authenticatedAt: null,
+                createdAt: null,
+                creationDate: null,
+                description: null,
+                gmsApiKey: null,
+                name: null,
                 updatedAt: null,
+                uuid: null,
+                federatedCommunities: [
+                  {
+                    id: 3,
+                    apiVersion: '2_0',
+                    endPoint: 'http://localhost/api/',
+                    createdAt: homeCom3.createdAt.toISOString(),
+                    lastAnnouncedAt: null,
+                    lastErrorAt: null,
+                    updatedAt: null,
+                    verifiedAt: null,
+                  },
+                  {
+                    id: 2,
+                    apiVersion: '1_1',
+                    endPoint: 'http://localhost/api/',
+                    createdAt: homeCom2.createdAt.toISOString(),
+                    lastAnnouncedAt: null,
+                    lastErrorAt: null,
+                    updatedAt: null,
+                    verifiedAt: null,
+                  },
+                  {
+                    id: 1,
+                    apiVersion: '1_0',
+                    endPoint: 'http://localhost/api/',
+                    createdAt: homeCom1.createdAt.toISOString(),
+                    lastAnnouncedAt: null,
+                    lastErrorAt: null,
+                    updatedAt: null,
+                    verifiedAt: null,
+                  },
+                ],
               },
             ],
           },
         })
       })
     })
-
-    describe('plus foreign-communities entries', () => {
-      beforeEach(async () => {
-        jest.clearAllMocks()
-
-        foreignCom1 = DbFederatedCommunity.create()
-        foreignCom1.foreign = true
-        foreignCom1.publicKey = Buffer.from(ed25519KeyPairStaticHex[3].public, 'hex')
-        foreignCom1.apiVersion = '1_0'
-        foreignCom1.endPoint = 'http://remotehost/api'
-        foreignCom1.createdAt = new Date()
-        await DbFederatedCommunity.insert(foreignCom1)
-
-        foreignCom2 = DbFederatedCommunity.create()
-        foreignCom2.foreign = true
-        foreignCom2.publicKey = Buffer.from(ed25519KeyPairStaticHex[4].public, 'hex')
-        foreignCom2.apiVersion = '1_1'
-        foreignCom2.endPoint = 'http://remotehost/api'
-        foreignCom2.createdAt = new Date()
-        await DbFederatedCommunity.insert(foreignCom2)
-
-        foreignCom3 = DbFederatedCommunity.create()
-        foreignCom3.foreign = true
-        foreignCom3.publicKey = Buffer.from(ed25519KeyPairStaticHex[5].public, 'hex')
-        foreignCom3.apiVersion = '2_0'
-        foreignCom3.endPoint = 'http://remotehost/api'
-        foreignCom3.createdAt = new Date()
-        await DbFederatedCommunity.insert(foreignCom3)
-      })
-
-      it('returns 3 home community and 3 foreign community entries', async () => {
-        await expect(query({ query: getCommunities })).resolves.toMatchObject({
-          data: {
-            getCommunities: [
-              {
-                id: 3,
-                foreign: homeCom3.foreign,
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[2].public),
-                endPoint: expect.stringMatching('http://localhost/api/'),
-                apiVersion: '2_0',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: homeCom3.createdAt.toISOString(),
-                updatedAt: null,
-              },
-              {
-                id: 2,
-                foreign: homeCom2.foreign,
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[1].public),
-                endPoint: expect.stringMatching('http://localhost/api/'),
-                apiVersion: '1_1',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: homeCom2.createdAt.toISOString(),
-                updatedAt: null,
-              },
-              {
-                id: 1,
-                foreign: homeCom1.foreign,
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[0].public),
-                endPoint: expect.stringMatching('http://localhost/api/'),
-                apiVersion: '1_0',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: homeCom1.createdAt.toISOString(),
-                updatedAt: null,
-              },
-              {
-                id: 6,
-                foreign: foreignCom3.foreign,
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[5].public),
-                endPoint: expect.stringMatching('http://remotehost/api/'),
-                apiVersion: '2_0',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: foreignCom3.createdAt.toISOString(),
-                updatedAt: null,
-              },
-              {
-                id: 5,
-                foreign: foreignCom2.foreign,
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[4].public),
-                endPoint: expect.stringMatching('http://remotehost/api/'),
-                apiVersion: '1_1',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: foreignCom2.createdAt.toISOString(),
-                updatedAt: null,
-              },
-              {
-                id: 4,
-                foreign: foreignCom1.foreign,
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[3].public),
-                endPoint: expect.stringMatching('http://remotehost/api/'),
-                apiVersion: '1_0',
-                lastAnnouncedAt: null,
-                verifiedAt: null,
-                lastErrorAt: null,
-                createdAt: foreignCom1.createdAt.toISOString(),
-                updatedAt: null,
-              },
-            ],
-          },
-        })
-      })
-    })
-
     describe('with 6 federated community entries', () => {
       let comHomeCom1: DbCommunity
       let comForeignCom1: DbCommunity
@@ -323,7 +227,6 @@ describe('CommunityResolver', () => {
       let foreignCom4: DbFederatedCommunity
 
       beforeEach(async () => {
-        jest.clearAllMocks()
         comHomeCom1 = DbCommunity.create()
         comHomeCom1.foreign = false
         comHomeCom1.url = 'http://localhost'
@@ -360,6 +263,30 @@ describe('CommunityResolver', () => {
         comForeignCom2.creationDate = new Date()
         await DbCommunity.insert(comForeignCom2)
 
+        foreignCom1 = DbFederatedCommunity.create()
+        foreignCom1.foreign = true
+        foreignCom1.publicKey = Buffer.from(ed25519KeyPairStaticHex[3].public, 'hex')
+        foreignCom1.apiVersion = '1_0'
+        foreignCom1.endPoint = 'http://remotehost/api'
+        foreignCom1.createdAt = new Date()
+        await DbFederatedCommunity.insert(foreignCom1)
+
+        foreignCom2 = DbFederatedCommunity.create()
+        foreignCom2.foreign = true
+        foreignCom2.publicKey = Buffer.from(ed25519KeyPairStaticHex[4].public, 'hex')
+        foreignCom2.apiVersion = '1_1'
+        foreignCom2.endPoint = 'http://remotehost/api'
+        foreignCom2.createdAt = new Date()
+        await DbFederatedCommunity.insert(foreignCom2)
+
+        foreignCom3 = DbFederatedCommunity.create()
+        foreignCom3.foreign = true
+        foreignCom3.publicKey = Buffer.from(ed25519KeyPairStaticHex[5].public, 'hex')
+        foreignCom3.apiVersion = '2_0'
+        foreignCom3.endPoint = 'http://remotehost/api'
+        foreignCom3.createdAt = new Date()
+        await DbFederatedCommunity.insert(foreignCom3)
+
         foreignCom4 = DbFederatedCommunity.create()
         foreignCom4.foreign = true
         foreignCom4.publicKey = Buffer.from(ed25519KeyPairStaticHex[5].public, 'hex')
@@ -376,15 +303,15 @@ describe('CommunityResolver', () => {
               {
                 foreign: false,
                 url: 'http://localhost',
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[2].public),
-                authenticatedAt: null,
-                createdAt: null,
-                creationDate: null,
-                description: null,
+                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[0].public),
+                authenticatedAt: comHomeCom1.authenticatedAt?.toISOString(),
+                createdAt: comHomeCom1.createdAt.toISOString(),
+                creationDate: comHomeCom1.creationDate?.toISOString(),
+                description: comHomeCom1.description,
                 gmsApiKey: null,
-                name: null,
+                name: comHomeCom1.name,
                 updatedAt: null,
-                uuid: null,
+                uuid: comHomeCom1.communityUuid,
                 federatedCommunities: [
                   {
                     id: 3,
@@ -396,21 +323,6 @@ describe('CommunityResolver', () => {
                     updatedAt: null,
                     verifiedAt: null,
                   },
-                ],
-              },
-              {
-                foreign: false,
-                url: 'http://localhost',
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[1].public),
-                authenticatedAt: null,
-                createdAt: null,
-                creationDate: null,
-                description: null,
-                gmsApiKey: null,
-                name: null,
-                updatedAt: null,
-                uuid: null,
-                federatedCommunities: [
                   {
                     id: 2,
                     apiVersion: '1_1',
@@ -421,21 +333,6 @@ describe('CommunityResolver', () => {
                     updatedAt: null,
                     verifiedAt: null,
                   },
-                ],
-              },
-              {
-                foreign: false,
-                url: 'http://localhost',
-                publicKey: expect.stringMatching(ed25519KeyPairStaticHex[0].public),
-                authenticatedAt: comHomeCom1.authenticatedAt?.toISOString(),
-                createdAt: comHomeCom1.createdAt.toISOString(),
-                creationDate: comHomeCom1.creationDate?.toISOString(),
-                description: comHomeCom1.description,
-                gmsApiKey: null,
-                name: comHomeCom1.name,
-                updatedAt: null,
-                uuid: comHomeCom1.communityUuid,
-                federatedCommunities: [
                   {
                     id: 1,
                     apiVersion: '1_0',
@@ -540,23 +437,21 @@ describe('CommunityResolver', () => {
     })
   })
 
-  describe('communities', () => {
+  describe('reachableCommunities', () => {
     let homeCom1: DbCommunity
     let foreignCom1: DbCommunity
     let foreignCom2: DbCommunity
 
-    describe('with empty list', () => {
-      beforeEach(async () => {
-        await cleanDB()
-        jest.clearAllMocks()
-      })
+    afterAll(async () => {
+      await DbCommunity.clear()
+      await DbFederatedCommunity.clear()
+    })
 
+    describe('with empty list', () => {
       it('returns no community entry', async () => {
-        // const result: Community[] = await query({ query: getCommunities })
-        // expect(result.length).toEqual(0)
-        await expect(query({ query: communitiesQuery })).resolves.toMatchObject({
+        await expect(query({ query: reachableCommunities })).resolves.toMatchObject({
           data: {
-            communities: [],
+            reachableCommunities: [],
           },
         })
       })
@@ -564,35 +459,20 @@ describe('CommunityResolver', () => {
 
     describe('with one home-community entry', () => {
       beforeEach(async () => {
-        await cleanDB()
-        jest.clearAllMocks()
-
-        homeCom1 = DbCommunity.create()
-        homeCom1.foreign = false
-        homeCom1.url = 'http://localhost/api'
-        homeCom1.publicKey = Buffer.from(ed25519KeyPairStaticHex[0].public, 'hex')
-        homeCom1.privateKey = Buffer.from(ed25519KeyPairStaticHex[0].private, 'hex')
-        homeCom1.communityUuid = 'HomeCom-UUID'
-        homeCom1.authenticatedAt = new Date()
-        homeCom1.name = 'HomeCommunity-name'
-        homeCom1.description = 'HomeCommunity-description'
-        homeCom1.creationDate = new Date()
+        homeCom1 = await createCommunity(false, false)
         await DbCommunity.insert(homeCom1)
       })
 
       it('returns 1 home-community entry', async () => {
-        await expect(query({ query: communitiesQuery })).resolves.toMatchObject({
+        await expect(query({ query: reachableCommunities })).resolves.toMatchObject({
           data: {
-            communities: [
+            reachableCommunities: [
               {
-                id: expect.any(Number),
                 foreign: homeCom1.foreign,
                 name: homeCom1.name,
                 description: homeCom1.description,
                 url: homeCom1.url,
-                creationDate: homeCom1.creationDate?.toISOString(),
                 uuid: homeCom1.communityUuid,
-                authenticatedAt: homeCom1.authenticatedAt?.toISOString(),
               },
             ],
           },
@@ -602,135 +482,55 @@ describe('CommunityResolver', () => {
 
     describe('returns 2 filtered communities even with 3 existing entries', () => {
       beforeEach(async () => {
-        await cleanDB()
-        jest.clearAllMocks()
-
-        homeCom1 = DbCommunity.create()
-        homeCom1.foreign = false
-        homeCom1.url = 'http://localhost/api'
-        homeCom1.publicKey = Buffer.from(ed25519KeyPairStaticHex[0].public, 'hex')
-        homeCom1.privateKey = Buffer.from(ed25519KeyPairStaticHex[0].private, 'hex')
-        homeCom1.communityUuid = 'HomeCom-UUID'
-        homeCom1.authenticatedAt = new Date()
-        homeCom1.name = 'HomeCommunity-name'
-        homeCom1.description = 'HomeCommunity-description'
-        homeCom1.creationDate = new Date()
-        await DbCommunity.insert(homeCom1)
-
-        foreignCom1 = DbCommunity.create()
-        foreignCom1.foreign = true
-        foreignCom1.url = 'http://stage-2.gradido.net/api'
-        foreignCom1.publicKey = Buffer.from(ed25519KeyPairStaticHex[3].public, 'hex')
-        foreignCom1.privateKey = Buffer.from(ed25519KeyPairStaticHex[3].private, 'hex')
-        // foreignCom1.communityUuid = 'Stage2-Com-UUID'
-        // foreignCom1.authenticatedAt = new Date()
-        foreignCom1.name = 'Stage-2_Community-name'
-        foreignCom1.description = 'Stage-2_Community-description'
-        foreignCom1.creationDate = new Date()
-        await DbCommunity.insert(foreignCom1)
-
-        foreignCom2 = DbCommunity.create()
-        foreignCom2.foreign = true
-        foreignCom2.url = 'http://stage-3.gradido.net/api'
-        foreignCom2.publicKey = Buffer.from(ed25519KeyPairStaticHex[4].public, 'hex')
-        foreignCom2.privateKey = Buffer.from(ed25519KeyPairStaticHex[4].private, 'hex')
-        foreignCom2.communityUuid = 'Stage3-Com-UUID'
-        foreignCom2.authenticatedAt = new Date()
-        foreignCom2.name = 'Stage-3_Community-name'
-        foreignCom2.description = 'Stage-3_Community-description'
-        foreignCom2.creationDate = new Date()
-        await DbCommunity.insert(foreignCom2)
+        foreignCom1 = await createCommunity(true, false)
+        foreignCom2 = await createCommunity(true, false)
+        const com1FedCom = await createVerifiedFederatedCommunity('1_0', 100, foreignCom1, false)
+        const com1FedCom2 = await createVerifiedFederatedCommunity('1_1', 100, foreignCom1, false)
+        const com2FedCom = await createVerifiedFederatedCommunity('1_0', 10000, foreignCom2, false)
+        await Promise.all([
+          DbCommunity.insert(foreignCom1),
+          DbCommunity.insert(foreignCom2),
+          DbFederatedCommunity.insert(com1FedCom),
+          DbFederatedCommunity.insert(com1FedCom2),
+          DbFederatedCommunity.insert(com2FedCom)
+        ])
       })
 
       it('returns 2 community entries', async () => {
-        await expect(query({ query: communitiesQuery })).resolves.toMatchObject({
-          data: {
-            communities: [
-              {
-                id: expect.any(Number),
-                foreign: homeCom1.foreign,
-                name: homeCom1.name,
-                description: homeCom1.description,
-                url: homeCom1.url,
-                creationDate: homeCom1.creationDate?.toISOString(),
-                uuid: homeCom1.communityUuid,
-                authenticatedAt: homeCom1.authenticatedAt?.toISOString(),
-              },
-              /*
-              {
-                id: expect.any(Number),
-                foreign: foreignCom1.foreign,
-                name: foreignCom1.name,
-                description: foreignCom1.description,
-                url: foreignCom1.url,
-                creationDate: foreignCom1.creationDate?.toISOString(),
-                uuid: foreignCom1.communityUuid,
-                authenticatedAt: foreignCom1.authenticatedAt?.toISOString(),
-              },
-              */
-              {
-                id: expect.any(Number),
-                foreign: foreignCom2.foreign,
-                name: foreignCom2.name,
-                description: foreignCom2.description,
-                url: foreignCom2.url,
-                creationDate: foreignCom2.creationDate?.toISOString(),
-                uuid: foreignCom2.communityUuid,
-                authenticatedAt: foreignCom2.authenticatedAt?.toISOString(),
-              },
-            ],
-          },
-        })
+        const result = await query({ query: reachableCommunities })
+        expect(result.data.reachableCommunities.length).toBe(2)
+        expect(result.data.reachableCommunities).toMatchObject([
+          {
+            foreign: homeCom1.foreign,
+            name: homeCom1.name,
+            description: homeCom1.description,
+            url: homeCom1.url,
+            uuid: homeCom1.communityUuid,
+          }, {
+            foreign: foreignCom1.foreign,
+            name: foreignCom1.name,
+            description: foreignCom1.description,
+            url: foreignCom1.url,
+            uuid: foreignCom1.communityUuid,
+          }
+        ])
       })
     })
 
     describe('search community by uuid', () => {
       let homeCom: DbCommunity | null
-      beforeEach(async () => {
-        await cleanDB()
-        jest.clearAllMocks()
-        const admin = await userFactory(testEnv, peterLustig)
-        // login as admin
-        await mutate({ mutation: login, variables: peterLoginData })
+      beforeAll(async () => {
+        await DbCommunity.clear()
 
-        // HomeCommunity is still created in userFactory
-        homeCom = await getCommunityByUuid(admin.communityUuid)
+        homeCom = await createCommunity(false, false)
+        foreignCom1 = await createCommunity(true, false)
+        foreignCom2 = await createCommunity(true, false)
 
-        foreignCom1 = DbCommunity.create()
-        foreignCom1.foreign = true
-        foreignCom1.url = 'http://stage-2.gradido.net/api'
-        foreignCom1.publicKey = Buffer.from(
-          '8a1f9374b99c30d827b85dcd23f7e50328430d64ef65ef35bf375ea8eb9a2e1d',
-          'hex',
-        )
-        foreignCom1.privateKey = Buffer.from(
-          'f6c2a9d78e20a3c910f35b8ffcf824aa7b37f0d3d81bfc4c0e65e17a194b3a4a',
-          'hex',
-        )
-        // foreignCom1.communityUuid = 'Stage2-Com-UUID'
-        // foreignCom1.authenticatedAt = new Date()
-        foreignCom1.name = 'Stage-2_Community-name'
-        foreignCom1.description = 'Stage-2_Community-description'
-        foreignCom1.creationDate = new Date()
-        await DbCommunity.insert(foreignCom1)
-
-        foreignCom2 = DbCommunity.create()
-        foreignCom2.foreign = true
-        foreignCom2.url = 'http://stage-3.gradido.net/api'
-        foreignCom2.publicKey = Buffer.from(
-          'e047365a54082e8a7e9273da61b55c8134a2a0c836799ba12b78b9b0c52bc85f',
-          'hex',
-        )
-        foreignCom2.privateKey = Buffer.from(
-          'e047365a54082e8a7e9273da61b55c8134a2a0c836799ba12b78b9b0c52bc85f',
-          'hex',
-        )
-        foreignCom2.communityUuid = uuidv4()
-        foreignCom2.authenticatedAt = new Date()
-        foreignCom2.name = 'Stage-3_Community-name'
-        foreignCom2.description = 'Stage-3_Community-description'
-        foreignCom2.creationDate = new Date()
-        await DbCommunity.insert(foreignCom2)
+        await Promise.all([
+          DbCommunity.insert(homeCom),
+          DbCommunity.insert(foreignCom1),
+          DbCommunity.insert(foreignCom2),
+        ])
       })
 
       it('finds the home-community by uuid', async () => {
@@ -749,7 +549,6 @@ describe('CommunityResolver', () => {
               url: homeCom?.url,
               creationDate: homeCom?.creationDate?.toISOString(),
               uuid: homeCom?.communityUuid,
-              authenticatedAt: homeCom?.authenticatedAt,
             },
           },
         })
@@ -769,76 +568,100 @@ describe('CommunityResolver', () => {
               description: homeCom?.description,
               url: homeCom?.url,
               creationDate: homeCom?.creationDate?.toISOString(),
-              uuid: homeCom?.communityUuid,
-              authenticatedAt: homeCom?.authenticatedAt,
+              uuid: homeCom?.communityUuid
             },
           },
         })
       })
-
-      it('updates the home-community gmsApiKey', async () => {
-        await expect(
-          mutate({
-            mutation: updateHomeCommunityQuery,
-            variables: { uuid: homeCom?.communityUuid, gmsApiKey: 'gmsApiKey' },
-          }),
-        ).resolves.toMatchObject({
-          data: {
-            updateHomeCommunity: {
-              id: expect.any(Number),
-              foreign: homeCom?.foreign,
-              name: homeCom?.name,
-              description: homeCom?.description,
-              url: homeCom?.url,
-              creationDate: homeCom?.creationDate?.toISOString(),
-              uuid: homeCom?.communityUuid,
-              authenticatedAt: homeCom?.authenticatedAt,
-              gmsApiKey: 'gmsApiKey',
-            },
-          },
-        })
-      })
-
-      it('throws error on updating a foreign-community', async () => {
-        expect(
-          await mutate({
-            mutation: updateHomeCommunityQuery,
-            variables: { uuid: foreignCom2.communityUuid, gmsApiKey: 'gmsApiKey' },
-          }),
-        ).toEqual(
-          expect.objectContaining({
-            errors: [new GraphQLError('Error: Only the HomeCommunity could be modified!')],
-          }),
-        )
-      })
-
-      it('throws error on updating a community without uuid', async () => {
-        expect(
-          await mutate({
-            mutation: updateHomeCommunityQuery,
-            variables: { uuid: null, gmsApiKey: 'gmsApiKey' },
-          }),
-        ).toEqual(
-          expect.objectContaining({
-            errors: [
-              new GraphQLError(`Variable "$uuid" of non-null type "String!" must not be null.`),
-            ],
-          }),
-        )
-      })
-
-      it('throws error on updating a community with not existing uuid', async () => {
-        expect(
-          await mutate({
-            mutation: updateHomeCommunityQuery,
-            variables: { uuid: uuidv4(), gmsApiKey: 'gmsApiKey' },
-          }),
-        ).toEqual(
-          expect.objectContaining({
-            errors: [new GraphQLError('HomeCommunity with uuid not found: ')],
-          }),
-        )
-      })
+    })
+  })
+
+  describe('update community', () => {
+    let homeCom: DbCommunity
+    let foreignCom1: DbCommunity
+    let foreignCom2: DbCommunity
+
+    beforeAll(async () => {
+      await DbCommunity.clear()
+
+      // create admin and login as admin
+      await userFactory(testEnv, peterLustig)      
+      homeCom = (await getHomeCommunity())!
+      foreignCom1 = await createCommunity(true, false)
+      foreignCom2 = await createCommunity(true, false)
+
+      await Promise.all([
+        DbCommunity.insert(foreignCom1),
+        DbCommunity.insert(foreignCom2),
+        mutate({ mutation: login, variables: peterLoginData })
+      ])
+    })
+
+    afterAll(async () => {
+      await cleanDB()
+    })
+
+    it('updates the home-community gmsApiKey', async () => {
+      await expect(
+        mutate({
+          mutation: updateHomeCommunityQuery,
+          variables: { uuid: homeCom?.communityUuid, gmsApiKey: 'gmsApiKey' },
+        }),
+      ).resolves.toMatchObject({
+        data: {
+          updateHomeCommunity: {
+            foreign: homeCom?.foreign,
+            name: homeCom?.name,
+            description: homeCom?.description,
+            url: homeCom?.url,
+            creationDate: homeCom?.creationDate?.toISOString(),
+            uuid: homeCom?.communityUuid,
+            authenticatedAt: homeCom?.authenticatedAt,
+            gmsApiKey: 'gmsApiKey',
+          },
+        },
+      })
+    })
+
+    it('throws error on updating a foreign-community', async () => {
+      expect(
+        await mutate({
+          mutation: updateHomeCommunityQuery,
+          variables: { uuid: foreignCom2.communityUuid, gmsApiKey: 'gmsApiKey' },
+        }),
+      ).toEqual(
+        expect.objectContaining({
+          errors: [new GraphQLError('Error: Only the HomeCommunity could be modified!')],
+        }),
+      )
+    })
+
+    it('throws error on updating a community without uuid', async () => {
+      expect(
+        await mutate({
+          mutation: updateHomeCommunityQuery,
+          variables: { uuid: null, gmsApiKey: 'gmsApiKey' },
+        }),
+      ).toEqual(
+        expect.objectContaining({
+          errors: [
+            new GraphQLError(`Variable "$uuid" of non-null type "String!" must not be null.`),
+          ],
+        }),
+      )
+    })
+
+    it('throws error on updating a community with not existing uuid', async () => {
+      expect(
+        await mutate({
+          mutation: updateHomeCommunityQuery,
+          variables: { uuid: uuidv4(), gmsApiKey: 'gmsApiKey' },
+        }),
+      ).toEqual(
+        expect.objectContaining({
+          errors: [new GraphQLError('HomeCommunity with uuid not found: ')],
+        }),
+      )
     })
   })
 })
diff --git a/backend/src/graphql/resolver/CommunityResolver.ts b/backend/src/graphql/resolver/CommunityResolver.ts
index a46e30144..675ec858f 100644
--- a/backend/src/graphql/resolver/CommunityResolver.ts
+++ b/backend/src/graphql/resolver/CommunityResolver.ts
@@ -1,12 +1,14 @@
-import { Community as DbCommunity, FederatedCommunity as DbFederatedCommunity, getHomeCommunity } from 'database'
+import { 
+  Community as DbCommunity, 
+  getReachableCommunities, 
+  getHomeCommunity 
+} from 'database'
 import { Arg, Args, Authorized, Mutation, Query, Resolver } from 'type-graphql'
-import { IsNull, Not } from 'typeorm'
 
 import { Paginated } from '@arg/Paginated'
 import { EditCommunityInput } from '@input/EditCommunityInput'
 import { AdminCommunityView } from '@model/AdminCommunityView'
 import { Community } from '@model/Community'
-import { FederatedCommunity } from '@model/FederatedCommunity'
 
 import { RIGHTS } from '@/auth/RIGHTS'
 import { LogError } from '@/server/LogError'
@@ -18,24 +20,11 @@ import {
   getCommunityByUuid,
 } from './util/communities'
 
+import { CONFIG } from '@/config'
+
 @Resolver()
 export class CommunityResolver {
-  @Authorized([RIGHTS.COMMUNITIES])
-  @Query(() => [FederatedCommunity])
-  async getCommunities(): Promise<FederatedCommunity[]> {
-    const dbFederatedCommunities: DbFederatedCommunity[] = await DbFederatedCommunity.find({
-      order: {
-        foreign: 'ASC',
-        createdAt: 'DESC',
-        lastAnnouncedAt: 'DESC',
-      },
-    })
-    return dbFederatedCommunities.map(
-      (dbCom: DbFederatedCommunity) => new FederatedCommunity(dbCom),
-    )
-  }
-
-  @Authorized([RIGHTS.COMMUNITIES])
+  @Authorized([RIGHTS.COMMUNITY_WITH_API_KEYS])
   @Query(() => [AdminCommunityView])
   async allCommunities(@Args() paginated: Paginated): Promise<AdminCommunityView[]> {
     // communityUUID could be oneTimePassCode (uint32 number)
@@ -44,17 +33,17 @@ export class CommunityResolver {
 
   @Authorized([RIGHTS.COMMUNITIES])
   @Query(() => [Community])
-  async communities(): Promise<Community[]> {
-    const dbCommunities: DbCommunity[] = await DbCommunity.find({
-      where: { communityUuid: Not(IsNull()) }, //, authenticatedAt: Not(IsNull()) },
-      order: {
-        name: 'ASC',
-      },
+  async reachableCommunities(): Promise<Community[]> {
+    const dbCommunities: DbCommunity[] = await getReachableCommunities(
+      CONFIG.FEDERATION_VALIDATE_COMMUNITY_TIMER * 2, {
+        // order by 
+        foreign: 'ASC', // home community first
+        name: 'ASC', // sort foreign communities by name
     })
     return dbCommunities.map((dbCom: DbCommunity) => new Community(dbCom))
   }
 
-  @Authorized([RIGHTS.COMMUNITY_BY_IDENTIFIER])
+  @Authorized([RIGHTS.COMMUNITIES])
   @Query(() => Community)
   async communityByIdentifier(
     @Arg('communityIdentifier') communityIdentifier: string,
@@ -67,7 +56,7 @@ export class CommunityResolver {
     return new Community(community)
   }
 
-  @Authorized([RIGHTS.HOME_COMMUNITY])
+  @Authorized([RIGHTS.COMMUNITIES])
   @Query(() => Community)
   async homeCommunity(): Promise<Community> {
     const community = await getHomeCommunity()
@@ -78,10 +67,10 @@ export class CommunityResolver {
   }
 
   @Authorized([RIGHTS.COMMUNITY_UPDATE])
-  @Mutation(() => Community)
+  @Mutation(() => AdminCommunityView)
   async updateHomeCommunity(
     @Args() { uuid, gmsApiKey, location, hieroTopicId }: EditCommunityInput,
-  ): Promise<Community> {
+  ): Promise<AdminCommunityView> {
     const homeCom = await getCommunityByUuid(uuid)
     if (!homeCom) {
       throw new LogError('HomeCommunity with uuid not found: ', uuid)
@@ -101,6 +90,6 @@ export class CommunityResolver {
       homeCom.hieroTopicId = hieroTopicId ?? null
       await DbCommunity.save(homeCom)
     }
-    return new Community(homeCom)
+    return new AdminCommunityView(homeCom)
   }
 }
diff --git a/backend/src/graphql/resolver/TransactionLinkResolver.ts b/backend/src/graphql/resolver/TransactionLinkResolver.ts
index 8acbd7b53..faae12e56 100644
--- a/backend/src/graphql/resolver/TransactionLinkResolver.ts
+++ b/backend/src/graphql/resolver/TransactionLinkResolver.ts
@@ -14,7 +14,7 @@ import { User } from '@model/User'
 import { QueryLinkResult } from '@union/QueryLinkResult'
 import { Decay, interpretEncryptedTransferArgs, TransactionTypeId } from 'core'
 import {
-  AppDatabase, Community as DbCommunity, Contribution as DbContribution,
+  AppDatabase, Contribution as DbContribution,
   ContributionLink as DbContributionLink, FederatedCommunity as DbFederatedCommunity, Transaction as DbTransaction,
   TransactionLink as DbTransactionLink,
   User as DbUser,
@@ -36,7 +36,7 @@ import { Context, getClientTimezoneOffset, getUser } from '@/server/context'
 import { calculateBalance } from '@/util/validate'
 import { fullName } from 'core'
 import { TRANSACTION_LINK_LOCK, TRANSACTIONS_LOCK } from 'database'
-import { calculateDecay, decode, DisburseJwtPayloadType, encode, encryptAndSign, EncryptedJWEJwtPayloadType, RedeemJwtPayloadType, verify } from 'shared'
+import { calculateDecay, compoundInterest, decayFormula, decode, DisburseJwtPayloadType, encode, encryptAndSign, EncryptedJWEJwtPayloadType, RedeemJwtPayloadType, verify } from 'shared'
 
 import { LOG4JS_BASE_CATEGORY_NAME } from '@/config/const'
 import { DisbursementClient as V1_0_DisbursementClient } from '@/federation/client/1_0/DisbursementClient'
@@ -48,7 +48,6 @@ import { randombytes_random } from 'sodium-native'
 import { executeTransaction } from './TransactionResolver'
 import {
   getAuthenticatedCommunities,
-  getCommunityByIdentifier,
   getCommunityByPublicKey,
   getCommunityByUuid,
 } from './util/communities'
@@ -90,7 +89,7 @@ export class TransactionLinkResolver {
     const createdDate = new Date()
     const validUntil = transactionLinkExpireDate(createdDate)
 
-    const holdAvailableAmount = amount.minus(calculateDecay(amount, createdDate, validUntil).decay)
+    const holdAvailableAmount = compoundInterest(amount, CODE_VALID_DAYS_DURATION * 24 * 60 * 60)
 
     // validate amount
     const sendBalance = await calculateBalance(user.id, holdAvailableAmount.mul(-1), createdDate)
diff --git a/backend/src/graphql/resolver/TransactionResolver.ts b/backend/src/graphql/resolver/TransactionResolver.ts
index c9d68de35..a61356e29 100644
--- a/backend/src/graphql/resolver/TransactionResolver.ts
+++ b/backend/src/graphql/resolver/TransactionResolver.ts
@@ -439,9 +439,7 @@ export class TransactionResolver {
     logger.debug(
       `sendCoins(recipientCommunityIdentifier=${recipientCommunityIdentifier}, recipientIdentifier=${recipientIdentifier}, amount=${amount}, memo=${memo})`,
     )
-    const homeCom = await DbCommunity.findOneOrFail({ where: { foreign: false } })
     const senderUser = getUser(context)
-
     if (!recipientCommunityIdentifier || (await isHomeCommunity(recipientCommunityIdentifier))) {
       // processing sendCoins within sender and recipient are both in home community
       const recipientUser = await findUserByIdentifier(
diff --git a/backend/src/graphql/resolver/UserResolver.ts b/backend/src/graphql/resolver/UserResolver.ts
index 045ca7756..e13391a55 100644
--- a/backend/src/graphql/resolver/UserResolver.ts
+++ b/backend/src/graphql/resolver/UserResolver.ts
@@ -1151,6 +1151,12 @@ export class UserResolver {
     @Args()
     { identifier, communityIdentifier }: UserArgs,
   ): Promise<User> {
+    // check if identifier contain community and user identifier
+    if (identifier.includes('/')) {
+      const parts = identifier.split('/')
+      communityIdentifier = parts[0]
+      identifier = parts[1]      
+    }
     const foundDbUser = await findUserByIdentifier(identifier, communityIdentifier)
     if (!foundDbUser) {
       createLogger().debug('User not found', identifier, communityIdentifier)
diff --git a/backend/src/seeds/graphql/mutations.ts b/backend/src/seeds/graphql/mutations.ts
index ec0a966a8..e42e738f2 100644
--- a/backend/src/seeds/graphql/mutations.ts
+++ b/backend/src/seeds/graphql/mutations.ts
@@ -375,7 +375,6 @@ export const logout = gql`
 export const updateHomeCommunityQuery = gql`
   mutation ($uuid: String!, $gmsApiKey: String!) {
     updateHomeCommunity(uuid: $uuid, gmsApiKey: $gmsApiKey) {
-      id
       foreign
       name
       description
diff --git a/backend/src/seeds/graphql/queries.ts b/backend/src/seeds/graphql/queries.ts
index 5a8e06cc0..2eb56e6f6 100644
--- a/backend/src/seeds/graphql/queries.ts
+++ b/backend/src/seeds/graphql/queries.ts
@@ -135,18 +135,14 @@ export const listGDTEntriesQuery = gql`
   }
 `
 
-export const communitiesQuery = gql`
-  query {
-    communities {
-      id
+export const reachableCommunities = gql`
+  query { 
+    reachableCommunities {
       foreign
+      uuid
       name
       description
       url
-      creationDate
-      uuid
-      authenticatedAt
-      gmsApiKey
     }
   }
 `
@@ -162,7 +158,6 @@ export const getCommunityByIdentifierQuery = gql`
       creationDate
       uuid
       authenticatedAt
-      gmsApiKey
     }
   }
 `
@@ -178,24 +173,6 @@ export const getHomeCommunityQuery = gql`
       creationDate
       uuid
       authenticatedAt
-      gmsApiKey
-    }
-  }
-`
-
-export const getCommunities = gql`
-  query {
-    getCommunities {
-      id
-      foreign
-      publicKey
-      endPoint
-      apiVersion
-      lastAnnouncedAt
-      verifiedAt
-      lastErrorAt
-      createdAt
-      updatedAt
     }
   }
 `
@@ -268,7 +245,7 @@ export const listContributions = gql`
   }
 `
 
-export const listAllContributions = `
+export const listAllContributions = gql`
 query ($pagination: Paginated!) {
   listAllContributions(pagination: $pagination) {
   	contributionCount
diff --git a/database/src/queries/communities.test.ts b/database/src/queries/communities.test.ts
index 9cfb210db..18975256c 100644
--- a/database/src/queries/communities.test.ts
+++ b/database/src/queries/communities.test.ts
@@ -1,8 +1,8 @@
-import { Community as DbCommunity } from '..'
+import { Community as DbCommunity, FederatedCommunity as DbFederatedCommunity } from '..'
 import { AppDatabase } from '../AppDatabase'
-import { getHomeCommunity } from './communities'
-import { describe, expect, it, beforeAll, afterAll } from 'vitest'
-import { createCommunity } from '../seeds/homeCommunity'
+import { getHomeCommunity, getReachableCommunities } from './communities'
+import { describe, expect, it, beforeEach, beforeAll, afterAll } from 'vitest'
+import { createCommunity, createVerifiedFederatedCommunity } from '../seeds/community'
 
 const db = AppDatabase.getInstance()
 
@@ -14,8 +14,10 @@ afterAll(async () => {
 })
 
 describe('community.queries', () => {
-  beforeAll(async () => {
+  // clean db for every test case
+  beforeEach(async () => {
     await DbCommunity.clear()
+    await DbFederatedCommunity.clear()
   })
   describe('getHomeCommunity', () => {
     it('should return null if no home community exists', async () => {
@@ -37,4 +39,51 @@ describe('community.queries', () => {
       expect(community?.privateKey).toStrictEqual(homeCom.privateKey)
     })
   })
+  describe('getReachableCommunities', () => {  
+    it('home community counts also to reachable communities', async () => {
+      await createCommunity(false)
+      expect(await getReachableCommunities(1000)).toHaveLength(1)
+    })
+    it('foreign communities authenticated within chosen range', async () => {
+      const com1 = await createCommunity(true)
+      const com2 = await createCommunity(true)
+      const com3 = await createCommunity(true)
+      await createVerifiedFederatedCommunity('1_0', 100, com1)
+      await createVerifiedFederatedCommunity('1_0', 500, com2)
+      // outside of range
+      await createVerifiedFederatedCommunity('1_0', 1200, com3)
+
+      const communities = await getReachableCommunities(1000)
+      expect(communities).toHaveLength(2)
+      expect(communities[0].communityUuid).toBe(com1.communityUuid)
+      expect(communities[1].communityUuid).toBe(com2.communityUuid)
+    })
+    it('multiple federated community api version, result in one community', async () => {
+      const com1 = await createCommunity(true)
+      await createVerifiedFederatedCommunity('1_0', 100, com1)
+      await createVerifiedFederatedCommunity('1_1', 100, com1)
+      expect(await getReachableCommunities(1000)).toHaveLength(1)
+    })
+    it('multiple federated community api version one outside of range, result in one community', async () => {
+      const com1 = await createCommunity(true)
+      await createVerifiedFederatedCommunity('1_0', 100, com1)
+      // outside of range
+      await createVerifiedFederatedCommunity('1_1', 1200, com1)
+      expect(await getReachableCommunities(1000)).toHaveLength(1)
+    })
+    it('foreign and home community', async () => {
+      // home community
+      await createCommunity(false)
+      const com1 = await createCommunity(true)
+      const com2 = await createCommunity(true)
+      await createVerifiedFederatedCommunity('1_0', 400, com1)
+      await createVerifiedFederatedCommunity('1_0', 1200, com2)
+      expect(await getReachableCommunities(1000)).toHaveLength(2)
+    })
+    it('not verified inside time frame federated community', async () => {
+      const com1 = await createCommunity(true)
+      await createVerifiedFederatedCommunity('1_0', 1200, com1)
+      expect(await getReachableCommunities(1000)).toHaveLength(0)
+    })
+  })
 })
\ No newline at end of file
diff --git a/database/src/queries/communities.ts b/database/src/queries/communities.ts
index edc3bd7ed..e216f8af6 100644
--- a/database/src/queries/communities.ts
+++ b/database/src/queries/communities.ts
@@ -1,10 +1,14 @@
+import { FindOptionsOrder, FindOptionsWhere, IsNull, MoreThanOrEqual, Not } from 'typeorm'
 import { Community as DbCommunity } from '../entity'
+import { urlSchema, uuidv4Schema } from 'shared'
 
 /**
  * Retrieves the home community, i.e., a community that is not foreign.
  * @returns A promise that resolves to the home community, or null if no home community was found
  */
 export async function getHomeCommunity(): Promise<DbCommunity | null> {
+  // TODO: Put in Cache, it is needed nearly always
+  // TODO: return only DbCommunity or throw to reduce unnecessary checks, because there should be always a home community
   return await DbCommunity.findOne({
     where: { foreign: false },
   })
@@ -15,3 +19,45 @@ export async function getCommunityByUuid(communityUuid: string): Promise<DbCommu
     where: [{ communityUuid }],
   })
 }
+
+export function findWithCommunityIdentifier(communityIdentifier: string): FindOptionsWhere<DbCommunity> {
+  const where: FindOptionsWhere<DbCommunity> = {}
+  // pre filter identifier type to reduce db query complexity
+  if (urlSchema.safeParse(communityIdentifier).success) {
+    where.url = communityIdentifier
+  } else if (uuidv4Schema.safeParse(communityIdentifier).success) {
+    where.communityUuid = communityIdentifier
+  } else {
+    where.name = communityIdentifier
+  }
+  return where
+}
+
+export async function getCommunityWithFederatedCommunityByIdentifier(
+  communityIdentifier: string,
+): Promise<DbCommunity | null> {
+  return await DbCommunity.findOne({
+    where: { ...findWithCommunityIdentifier(communityIdentifier) },
+    relations: ['federatedCommunities'],
+  })
+}
+
+// returns all reachable communities 
+// home community and all federated communities which have been verified within the last authenticationTimeoutMs
+export async function getReachableCommunities(
+  authenticationTimeoutMs: number,
+  order?: FindOptionsOrder<DbCommunity>
+): Promise<DbCommunity[]> {
+  return await DbCommunity.find({
+    where: [ 
+      { 
+        authenticatedAt: Not(IsNull()), 
+        federatedCommunities: { 
+          verifiedAt: MoreThanOrEqual(new Date(Date.now() - authenticationTimeoutMs)) 
+        } 
+      },
+      { foreign: false },
+    ],
+    order,
+  })
+}
\ No newline at end of file
diff --git a/database/src/queries/pendingTransactions.test.ts b/database/src/queries/pendingTransactions.test.ts
index 72deaac71..c59c312e4 100644
--- a/database/src/queries/pendingTransactions.test.ts
+++ b/database/src/queries/pendingTransactions.test.ts
@@ -14,7 +14,7 @@ import { peterLustig } from '../seeds/users/peter-lustig'
 import { bobBaumeister } from '../seeds/users/bob-baumeister'
 import { garrickOllivander } from '../seeds/users/garrick-ollivander'
 import { describe, expect, it, beforeAll, afterAll } from 'vitest'
-import { createCommunity } from '../seeds/homeCommunity'
+import { createCommunity } from '../seeds/community'
 import { v4 as uuidv4 } from 'uuid'
 import Decimal from 'decimal.js-light'
 
diff --git a/database/src/queries/user.test.ts b/database/src/queries/user.test.ts
index 8cb95e0ac..873ca7a2b 100644
--- a/database/src/queries/user.test.ts
+++ b/database/src/queries/user.test.ts
@@ -4,7 +4,7 @@ import { aliasExists, findUserByIdentifier } from './user'
 import { userFactory } from '../seeds/factory/user'
 import { bibiBloxberg } from '../seeds/users/bibi-bloxberg'
 import { describe, expect, it, beforeAll, afterAll, beforeEach, } from 'vitest'
-import { createCommunity } from '../seeds/homeCommunity'
+import { createCommunity } from '../seeds/community'
 import { peterLustig } from '../seeds/users/peter-lustig'
 import { bobBaumeister } from '../seeds/users/bob-baumeister'
 import { getLogger, printLogs, clearLogs } from '../../../config-schema/test/testSetup.vitest'
diff --git a/database/src/queries/user.ts b/database/src/queries/user.ts
index 2cb0eaaee..d7083e8aa 100644
--- a/database/src/queries/user.ts
+++ b/database/src/queries/user.ts
@@ -1,9 +1,8 @@
 import { Raw } from 'typeorm'
-import { Community, User as DbUser, UserContact as DbUserContact } from '../entity'
-import { FindOptionsWhere } from 'typeorm'
-import { aliasSchema, emailSchema, uuidv4Schema, urlSchema } from 'shared'
+import { User as DbUser, UserContact as DbUserContact } from '../entity'
+import { aliasSchema, emailSchema, uuidv4Schema } from 'shared'
 import { getLogger } from 'log4js'
-import { LOG4JS_QUERIES_CATEGORY_NAME } from './index'
+import { findWithCommunityIdentifier, LOG4JS_QUERIES_CATEGORY_NAME } from './index'
 
 export async function aliasExists(alias: string): Promise<boolean> {
   const user = await DbUser.findOne({
@@ -22,11 +21,9 @@ export const findUserByIdentifier = async (
   identifier: string,
   communityIdentifier?: string,
 ): Promise<DbUser | null> => {
-  const communityWhere: FindOptionsWhere<Community> = urlSchema.safeParse(communityIdentifier).success
-    ? { url: communityIdentifier }
-    : uuidv4Schema.safeParse(communityIdentifier).success
-      ? { communityUuid: communityIdentifier }
-      : { name: communityIdentifier }
+  const communityWhere = communityIdentifier 
+    ? findWithCommunityIdentifier(communityIdentifier) 
+    : undefined
 
   if (uuidv4Schema.safeParse(identifier).success) {
     return DbUser.findOne({
diff --git a/database/src/seeds/community.ts b/database/src/seeds/community.ts
new file mode 100644
index 000000000..4db872398
--- /dev/null
+++ b/database/src/seeds/community.ts
@@ -0,0 +1,42 @@
+import { Community, FederatedCommunity } from '../entity'
+import { randomBytes } from 'node:crypto'
+import { v4 as uuidv4 } from 'uuid'
+
+export async function createCommunity(foreign: boolean, save: boolean = true): Promise<Community> {
+    const community = new Community()    
+    community.publicKey = randomBytes(32)
+    community.communityUuid = uuidv4()
+    community.name = 'HomeCommunity-name'
+    community.creationDate = new Date()
+
+    if(foreign) {
+        community.foreign = true
+        community.name = 'ForeignCommunity-name'
+        community.description = 'ForeignCommunity-description'
+        community.url = `http://foreign-${Math.random()}/api`
+        community.authenticatedAt = new Date()
+    } else {
+        community.foreign = false
+        // todo: generate valid public/private key pair (ed25519)
+        community.privateKey = randomBytes(64)
+        community.name = 'HomeCommunity-name'
+        community.description = 'HomeCommunity-description'
+        community.url = 'http://localhost/api'
+    }
+    return save ? await community.save() : community
+}
+
+export async function createVerifiedFederatedCommunity(
+    apiVersion: string,
+    verifiedBeforeMs: number,
+    community: Community,
+    save: boolean = true
+): Promise<FederatedCommunity> {
+    const federatedCommunity = new FederatedCommunity()
+    federatedCommunity.apiVersion = apiVersion
+    federatedCommunity.endPoint = community.url
+    federatedCommunity.publicKey = community.publicKey
+    federatedCommunity.community = community
+    federatedCommunity.verifiedAt = new Date(Date.now() - verifiedBeforeMs)
+    return save ? await federatedCommunity.save() : federatedCommunity
+}
diff --git a/database/src/seeds/homeCommunity.ts b/database/src/seeds/homeCommunity.ts
deleted file mode 100644
index d76ee0b98..000000000
--- a/database/src/seeds/homeCommunity.ts
+++ /dev/null
@@ -1,26 +0,0 @@
-import { Community } from '../entity'
-import { randomBytes } from 'node:crypto'
-import { v4 as uuidv4 } from 'uuid'
-
-export async function createCommunity(foreign: boolean): Promise<Community> {
-    const homeCom = new Community()    
-    homeCom.publicKey = randomBytes(32)
-    homeCom.communityUuid = uuidv4()
-    homeCom.authenticatedAt = new Date()
-    homeCom.name = 'HomeCommunity-name'
-    homeCom.creationDate = new Date()
-
-    if(foreign) {
-        homeCom.foreign = true
-        homeCom.name = 'ForeignCommunity-name'
-        homeCom.description = 'ForeignCommunity-description'
-        homeCom.url = 'http://foreign/api'
-    } else {
-        homeCom.foreign = false
-        homeCom.privateKey = randomBytes(64)
-        homeCom.name = 'HomeCommunity-name'
-        homeCom.description = 'HomeCommunity-description'
-        homeCom.url = 'http://localhost/api'
-    }
-    return await homeCom.save()
-}
diff --git a/frontend/src/components/CommunitySwitch.vue b/frontend/src/components/CommunitySwitch.vue
index b081f5d93..e0ef393d1 100644
--- a/frontend/src/components/CommunitySwitch.vue
+++ b/frontend/src/components/CommunitySwitch.vue
@@ -22,10 +22,10 @@
 </template>
 
 <script setup>
-import { ref, computed, onMounted } from 'vue'
+import { ref, computed, onMounted, watch } from 'vue'
 import { useQuery } from '@vue/apollo-composable'
 import { useRoute } from 'vue-router'
-import { selectCommunities } from '@/graphql/queries'
+import { reachableCommunities } from '@/graphql/communities.graphql'
 import { useAppToast } from '@/composables/useToast'
 
 const props = defineProps({
@@ -33,9 +33,13 @@ const props = defineProps({
     type: Object,
     default: () => ({}),
   },
+  communityIdentifier: {
+    type: String,
+    default: '',
+  },
 })
 
-const emit = defineEmits(['update:modelValue'])
+const emit = defineEmits(['update:modelValue', 'communitiesLoaded'])
 
 const route = useRoute()
 const { toastError } = useAppToast()
@@ -43,20 +47,31 @@ const { toastError } = useAppToast()
 const communities = ref([])
 const validCommunityIdentifier = ref(false)
 
-const { onResult } = useQuery(selectCommunities)
+const { onResult } = useQuery(reachableCommunities)
 
 onResult(({ data }) => {
   // console.log('CommunitySwitch.onResult...data=', data)
   if (data) {
-    communities.value = data.communities
+    communities.value = data.reachableCommunities
     setDefaultCommunity()
-    if (data.communities.length === 1) {
+    if (data.reachableCommunities.length === 1) {
       validCommunityIdentifier.value = true
     }
+    emit('communitiesLoaded', data.reachableCommunities)
   }
 })
 
-const communityIdentifier = computed(() => route.params.communityIdentifier)
+const communityIdentifier = computed(
+  () => route.params.communityIdentifier || props.communityIdentifier,
+)
+
+watch(
+  () => communityIdentifier.value,
+  () => {
+    // console.log('CommunitySwitch.communityIdentifier.value', value)
+    setDefaultCommunity()
+  },
+)
 
 function updateCommunity(community) {
   // console.log('CommunitySwitch.updateCommunity...community=', community)
diff --git a/frontend/src/components/Contributions/ContributionForm.vue b/frontend/src/components/Contributions/ContributionForm.vue
index 402d37f43..2161306ee 100644
--- a/frontend/src/components/Contributions/ContributionForm.vue
+++ b/frontend/src/components/Contributions/ContributionForm.vue
@@ -165,18 +165,35 @@ const validationSchema = computed(() => {
       .required('form.validation.contributionMemo.required'),
     hours: string()
       .typeError({ key: 'form.validation.hours.typeError', values: { min: 0.01, max: maxHours } })
-      .required()
       .transform((currentValue) =>
         !currentValue || typeof currentValue !== 'string'
           ? currentValue
           : currentValue.replace(',', '.'),
       )
+      // min and max are needed for html min max which validatedInput will take from this scheme
       .min(0.01, ({ min }) => ({ key: 'form.validation.hours.min', values: { min } }))
       .max(maxHours, ({ max }) => ({ key: 'form.validation.hours.max', values: { max } }))
       .test('decimal-places', 'form.validation.hours.decimal-places', (value) => {
         if (value === undefined || value === null) return true
         return /^\d+(\.\d{0,2})?$/.test(value.toString())
-      }),
+      })
+      // min and max are not working with string, so we need to do it manually
+      .test('min-hours', { key: 'form.validation.hours.min', values: { min: 0.01 } }, (value) => {
+        if (value === undefined || value === null || Number.isNaN(parseFloat(value))) {
+          return false
+        }
+        return parseFloat(value) >= 0.01
+      })
+      .test(
+        'max-hours',
+        { key: 'form.validation.hours.max', values: { max: maxHours } },
+        (value) => {
+          if (value === undefined || value === null || Number.isNaN(parseFloat(value))) {
+            return false
+          }
+          return parseFloat(value) <= maxHours
+        },
+      ),
     amount: number().min(0.01).max(maxAmounts),
   })
 })
diff --git a/frontend/src/components/GddSend/TransactionConfirmationLink.vue b/frontend/src/components/GddSend/TransactionConfirmationLink.vue
index f31d043a0..d964f3e80 100644
--- a/frontend/src/components/GddSend/TransactionConfirmationLink.vue
+++ b/frontend/src/components/GddSend/TransactionConfirmationLink.vue
@@ -20,20 +20,29 @@
         <BCol>{{ $t('advanced-calculation') }}</BCol>
       </BRow>
       <BRow class="pe-3" offset="2">
-        <BCol offset="2">{{ $t('form.current_balance') }}</BCol>
+        <BCol offset="2">{{ $t('form.current_available') }}</BCol>
         <BCol>{{ $filters.GDD(balance) }}</BCol>
       </BRow>
       <BRow class="pe-3">
         <BCol offset="2">
-          <strong>{{ $t('form.your_amount') }}</strong>
+          <strong>{{ $t('form.link_amount') }}</strong>
         </BCol>
-        <BCol class="borderbottom">
+        <BCol>
           <strong>{{ $filters.GDD(amount * -1) }}</strong>
         </BCol>
       </BRow>
       <BRow class="pe-3">
-        <BCol offset="2">{{ $t('form.new_balance') }}</BCol>
-        <BCol>{{ $filters.GDD(balance - amount) }}</BCol>
+        <BCol offset="2">{{ $t('decay.decay') }}</BCol>
+        <BCol class="borderbottom">{{ $filters.GDD(amount - blockedAmount) }}</BCol>
+      </BRow>
+      <BRow class="pe-3">
+        <BCol offset="2">{{ $t('form.available_after') }}</BCol>
+        <BCol>{{ $filters.GDD(balance - blockedAmount) }}</BCol>
+      </BRow>
+      <BRow class="pe-6 mt-2">
+        <BCol offset="1">
+          <small>{{ $t('form.link_decay_description') }}</small>
+        </BCol>
       </BRow>
       <BRow class="mt-5">
         <BCol cols="12" md="6" lg="6">
@@ -57,6 +66,7 @@
   </div>
 </template>
 <script>
+import { LINK_COMPOUND_INTEREST_FACTOR } from '@/constants'
 export default {
   name: 'TransactionConfirmationLink',
   props: {
@@ -68,7 +78,13 @@ export default {
   },
   computed: {
     totalBalance() {
-      return this.balance - this.amount * 1.028
+      return this.balance - this.blockedAmount
+    },
+    blockedAmount() {
+      // correct formula
+      return this.amount * LINK_COMPOUND_INTEREST_FACTOR
+      // same formula as in backend
+      // return 2 * this.amount - this.amount * Math.pow(0.99999997803504048, 1209600)
     },
     disabled() {
       if (this.totalBalance < 0) {
diff --git a/frontend/src/components/GddSend/TransactionForm.spec.js b/frontend/src/components/GddSend/TransactionForm.spec.js
index 5bd9e9d8e..afaf36b6f 100644
--- a/frontend/src/components/GddSend/TransactionForm.spec.js
+++ b/frontend/src/components/GddSend/TransactionForm.spec.js
@@ -26,6 +26,7 @@ vi.mock('vue-router', () => ({
 }))
 
 const mockUseQuery = vi.fn()
+const mockUseLazyQuery = vi.fn()
 vi.mock('@vue/apollo-composable', () => ({
   useQuery: (...args) => {
     mockUseQuery(...args)
@@ -35,6 +36,12 @@ vi.mock('@vue/apollo-composable', () => ({
       error: ref(null),
     }
   },
+  useLazyQuery: (...args) => {
+    mockUseLazyQuery(...args)
+    return {
+      refetch: vi.fn(() => true),
+    }
+  },
 }))
 
 vi.mock('@/composables/useToast', () => ({
diff --git a/frontend/src/components/GddSend/TransactionForm.vue b/frontend/src/components/GddSend/TransactionForm.vue
index 8d977b835..7ce3ac68f 100644
--- a/frontend/src/components/GddSend/TransactionForm.vue
+++ b/frontend/src/components/GddSend/TransactionForm.vue
@@ -48,7 +48,9 @@
                         <community-switch
                           :disabled="isBalanceEmpty"
                           :model-value="form.targetCommunity"
+                          :community-identifier="autoCommunityIdentifier"
                           @update:model-value="updateField($event, 'targetCommunity')"
+                          @communities-loaded="setCommunities"
                         />
                       </BCol>
                     </BRow>
@@ -62,7 +64,7 @@
                         :label="$t('form.recipient')"
                         :placeholder="$t('form.identifier')"
                         :rules="validationSchema.fields.identifier"
-                        :disabled="isBalanceEmpty"
+                        :disabled="isBalanceEmpty || isCommunitiesEmpty"
                         :disable-smart-valid-state="disableSmartValidState"
                         @update:model-value="updateField"
                       />
@@ -171,6 +173,8 @@ const props = defineProps({
 const entityDataToForm = computed(() => ({ ...props }))
 const form = reactive({ ...entityDataToForm.value })
 const disableSmartValidState = ref(false)
+const communities = ref([])
+const autoCommunityIdentifier = ref('')
 
 const emit = defineEmits(['set-transaction'])
 
@@ -191,6 +195,10 @@ const userIdentifier = computed(() => {
   return null
 })
 
+function setCommunities(returnedCommunities) {
+  communities.value = returnedCommunities
+}
+
 const validationSchema = computed(() => {
   const amountSchema = number()
     .required()
@@ -214,7 +222,24 @@ const validationSchema = computed(() => {
     return object({
       memo: memoSchema,
       amount: amountSchema,
-      identifier: identifierSchema,
+      identifier: identifierSchema.test(
+        'community-is-reachable',
+        'form.validation.identifier.communityIsReachable',
+        (value) => {
+          const parts = value.split('/')
+          // early exit if no community id is in identifier string
+          if (parts.length !== 2) {
+            return true
+          }
+          return communities.value.some((community) => {
+            return (
+              community.uuid === parts[0] ||
+              community.name === parts[0] ||
+              community.url === parts[0]
+            )
+          })
+        },
+      ),
     })
   } else {
     // don't need identifier schema if it is a transaction link or identifier was set via url
@@ -224,7 +249,6 @@ const validationSchema = computed(() => {
     })
   }
 })
-
 const formIsInvalid = computed(() => !validationSchema.value.isValidSync(form))
 
 const updateField = (newValue, name) => {
@@ -234,6 +258,7 @@ const updateField = (newValue, name) => {
 }
 
 const isBalanceEmpty = computed(() => props.balance <= 0)
+const isCommunitiesEmpty = computed(() => communities.value.length === 0)
 
 const { result: userResult, error: userError } = useQuery(
   user,
@@ -258,8 +283,35 @@ watch(userError, (error) => {
   }
 })
 
+// if identifier contain valid community identifier of a reachable community:
+// set it as target community and change community-switch to show only current value, instead of select
+watch(
+  () => form.identifier,
+  (value) => {
+    autoCommunityIdentifier.value = ''
+    const parts = value.split('/')
+    if (parts.length === 2) {
+      const com = communities.value.find(
+        (community) =>
+          community.uuid === parts[0] || community.name === parts[0] || community.url === parts[0],
+      )
+      if (com) {
+        form.targetCommunity = com
+        autoCommunityIdentifier.value = com.uuid
+      }
+    }
+  },
+)
+
 function onSubmit() {
   const transformedForm = validationSchema.value.cast(form)
+  const parts = transformedForm.identifier.split('/')
+  if (parts.length === 2) {
+    transformedForm.identifier = parts[1]
+    transformedForm.targetCommunity = communities.value.find((com) => {
+      return com.uuid === parts[0] || com.name === parts[0] || com.url === parts[0]
+    })
+  }
   emit('set-transaction', {
     ...transformedForm,
     selected: radioSelected.value,
diff --git a/frontend/src/constants.js b/frontend/src/constants.js
index f53926e91..33d654f7e 100644
--- a/frontend/src/constants.js
+++ b/frontend/src/constants.js
@@ -1,2 +1,5 @@
 export const GDD_PER_HOUR = 20
 export const PAGE_SIZE = 25
+// compound interest factor (decay reversed) for 14 days (hard coded backend link timeout)
+// 365.2425 days per year (gregorian calendar year)
+export const LINK_COMPOUND_INTEREST_FACTOR = Math.pow(2, 14 / 365.2425)
diff --git a/frontend/src/graphql/communities.graphql b/frontend/src/graphql/communities.graphql
new file mode 100644
index 000000000..140ade42e
--- /dev/null
+++ b/frontend/src/graphql/communities.graphql
@@ -0,0 +1,9 @@
+query reachableCommunities {
+  reachableCommunities {
+    foreign
+    uuid
+    name
+    description
+    url
+  }
+}
\ No newline at end of file
diff --git a/frontend/src/graphql/queries.js b/frontend/src/graphql/queries.js
index 52c7c89b2..e760ccb9f 100644
--- a/frontend/src/graphql/queries.js
+++ b/frontend/src/graphql/queries.js
@@ -91,19 +91,6 @@ export const listGDTEntriesQuery = gql`
     }
   }
 `
-
-export const selectCommunities = gql`
-  query {
-    communities {
-      uuid
-      name
-      description
-      foreign
-      url
-    }
-  }
-`
-
 export const queryOptIn = gql`
   query ($optIn: String!) {
     queryOptIn(optIn: $optIn)
diff --git a/frontend/src/graphql/user.graphql b/frontend/src/graphql/user.graphql
index c8617172f..0da877f2f 100644
--- a/frontend/src/graphql/user.graphql
+++ b/frontend/src/graphql/user.graphql
@@ -3,4 +3,10 @@ fragment userFields on User {
   firstName
   lastName
   alias
-}
\ No newline at end of file
+}
+
+query user($identifier: String!, $communityIdentifier: String) {
+  user(identifier: $identifier, communityIdentifier: $communityIdentifier) {
+    ...userFields
+  }
+}
diff --git a/frontend/src/locales/de.json b/frontend/src/locales/de.json
index 5cfc2740d..f57a9ef5f 100644
--- a/frontend/src/locales/de.json
+++ b/frontend/src/locales/de.json
@@ -164,10 +164,12 @@
   "form": {
     "amount": "Betrag",
     "at": "am",
+    "available_after": "Verfügbar nach Bestätigung",
     "cancel": "Abbrechen",
     "change": "Ändern",
     "check_now": "Jetzt prüfen",
     "close": "Schließen",
+    "current_available": "Aktuell verfügbar",
     "current_balance": "Aktueller Kontostand",
     "date": "Datum",
     "description": "Beschreibung",
@@ -178,6 +180,8 @@
     "hours": "Stunden",
     "identifier": "Email, Nutzername oder Gradido ID",
     "lastname": "Nachname",
+    "link_amount": "Link-Betrag",
+    "link_decay_description": "Der Link-Betrag wird zusammen mit der maximalen Vergänglichkeit blockiert. Nach Einlösen, Verfallen oder Löschen des Links wird der Rest wieder freigegeben.",
     "memo": "Nachricht",
     "message": "Nachricht",
     "new_balance": "Neuer Kontostand nach Bestätigung",
@@ -231,6 +235,7 @@
       },
       "gddSendAmount": "Das Feld {_field_} muss eine Zahl zwischen {min} und {max} mit höchstens zwei Nachkommastellen sein.",
       "identifier": {
+        "communityIsReachable": "Community nicht gefunden oder nicht erreichbar!",
         "required": "Der Empfänger ist ein Pflichtfeld.",
         "typeError": "Der Empfänger muss eine Email, ein Nutzernamen oder eine Gradido ID sein."
       },
diff --git a/frontend/src/locales/en.json b/frontend/src/locales/en.json
index bd3f91dfd..d127d4119 100644
--- a/frontend/src/locales/en.json
+++ b/frontend/src/locales/en.json
@@ -164,10 +164,12 @@
   "form": {
     "amount": "Amount",
     "at": "at",
+    "available_after": "Available after confirmation",
     "cancel": "Cancel",
     "change": "Change",
     "check_now": "Check now",
     "close": "Close",
+    "current_available": "Currently available",
     "current_balance": "Current Balance",
     "date": "Date",
     "description": "Description",
@@ -178,6 +180,8 @@
     "hours": "Hours",
     "identifier": "Email, username or gradido ID",
     "lastname": "Lastname",
+    "link_amount": "Link amount",
+    "link_decay_description": "The link amount is blocked along with the maximum decay. After the link has been redeemed, expired, or deleted, the rest is released again.",
     "memo": "Message",
     "message": "Message",
     "new_balance": "Account balance after confirmation",
@@ -231,6 +235,7 @@
       },
       "gddSendAmount": "The {_field_} field must be a number between {min} and {max} with at most two digits after the decimal point.",
       "identifier": {
+        "communityIsReachable": "Community not found our not reachable!",
         "required": "The recipient is a required field.",
         "typeError": "The recipient must be an email, a username or a Gradido ID."
       },
diff --git a/frontend/src/locales/es.json b/frontend/src/locales/es.json
index 23d6c1237..47027609f 100644
--- a/frontend/src/locales/es.json
+++ b/frontend/src/locales/es.json
@@ -146,10 +146,12 @@
   "form": {
     "amount": "Importe",
     "at": "am",
+    "available_after": "Disponible tras la confirmación",
     "cancel": "Cancelar",
     "change": "Cambiar",
     "check_now": "Revisar",
     "close": "Cerrar",
+    "current_available": "Actualmente disponible",
     "current_balance": "Saldo de cuenta actual",
     "date": "Fecha",
     "description": "Descripción",
@@ -158,6 +160,8 @@
     "from": "De",
     "generate_now": "crear ahora",
     "lastname": "Apellido",
+    "link_amount": "Importe del enlace",
+    "link_decay_description": "El importe del enlace se bloquea junto con la ransience máxima. Una vez que el enlace se ha canjeado, caducado o eliminado, el resto se libera de nuevo.",
     "memo": "Mensaje",
     "message": "Noticia",
     "new_balance": "Saldo de cuenta nuevo depués de confirmación",
@@ -185,6 +189,11 @@
     "to1": "para",
     "validation": {
       "gddSendAmount": "El campo {_field_} debe ser un número entre {min} y {max} con un máximo de dos decimales",
+      "identifier": {
+        "communityIsReachable": "Comunidad no encontrada o no alcanzable!",
+        "required": "El destinatario es un campo obligatorio.",
+        "typeError": "El destinatario debe ser un email, un nombre de usuario o un Gradido ID."
+      },
       "is-not": "No es posible  transferirte Gradidos a ti mismo",
       "requiredField": "El campo {fieldName} es obligatorio",
       "usernmae-regex": "El nombre de usuario debe comenzar con una letra seguida de al menos dos caracteres alfanuméricos.",
diff --git a/frontend/src/locales/fr.json b/frontend/src/locales/fr.json
index c2c87e976..3fa6da270 100644
--- a/frontend/src/locales/fr.json
+++ b/frontend/src/locales/fr.json
@@ -151,10 +151,12 @@
   "form": {
     "amount": "Montant",
     "at": "à",
+    "available_after": "Disponible après confirmation",
     "cancel": "Annuler",
     "change": "Changer",
     "check_now": "Vérifier maintenant",
     "close": "Fermer",
+    "current_available": "Actuellement disponible",
     "current_balance": "Solde actuel",
     "date": "Date",
     "description": "Description",
@@ -164,6 +166,8 @@
     "generate_now": "Produire maintenant",
     "hours": "Heures",
     "lastname": "Nom",
+    "link_amount": "Montant du lien",
+    "link_decay_description": "Le montant du lien est bloqué avec le dépérissement maximale. Une fois le lien utilisé, expiré ou supprimé, le reste est à nouveau débloqué.",
     "memo": "Note",
     "message": "Message",
     "new_balance": "Montant du solde après confirmation",
@@ -191,6 +195,11 @@
     "validation": {
       "gddCreationTime": "Le champ {_field_} doit comprendre un nombre entre {min} et {max} avec un maximum de une décimale.",
       "gddSendAmount": "Le champ {_field_} doit comprendre un nombre entre {min} et {max} avec un maximum de deux chiffres après la virgule",
+      "identifier": {
+        "communityIsReachable": "Communauté non joignable!",
+        "required": "Le destinataire est un champ obligatoire.",
+        "typeError": "Le destinataire doit être un email, un nom d'utilisateur ou un Gradido ID."
+      },
       "is-not": "Vous ne pouvez pas vous envoyer de Gradido à vous-même",
       "requiredField": "Le champ {fieldName} est obligatoire",
       "usernmae-regex": "Le nom d'utilisateur doit commencer par une lettre, suivi d'au moins deux caractères alphanumériques.",
diff --git a/frontend/src/locales/nl.json b/frontend/src/locales/nl.json
index 2d47d64c7..4cc86283a 100644
--- a/frontend/src/locales/nl.json
+++ b/frontend/src/locales/nl.json
@@ -146,10 +146,12 @@
   "form": {
     "amount": "Bedrag",
     "at": "op",
+    "available_after": "Beschikbaar na bevestiging",
     "cancel": "Annuleren",
     "change": "Wijzigen",
     "check_now": "Nu controleren",
     "close": "Sluiten",
+    "current_available": "Momenteel beschikbaar",
     "current_balance": "Actueel banksaldo",
     "date": "Datum",
     "description": "Beschrijving",
@@ -158,6 +160,8 @@
     "from": "Van",
     "generate_now": "Nu genereren",
     "lastname": "Achternaam",
+    "link_amount": "Linkbedrag",
+    "link_decay_description": "Het linkbedrag wordt geblokkeerd samen met de maximale vergankelijkheid. Nadat de link is ingewisseld, verlopen of verwijderd, wordt het resterende bedrag weer vrijgegeven.",
     "memo": "Memo",
     "message": "Bericht",
     "new_balance": "Nieuw banksaldo na bevestiging",
@@ -185,6 +189,11 @@
     "to1": "aan",
     "validation": {
       "gddSendAmount": "Het veld {_field_} moet een getal tussen {min} en {max} met maximaal twee cijfers achter de komma zijn",
+      "identifier": {
+        "communityIsReachable": "Community niet gevonden of niet bereikbaar!",
+        "required": "Ontvanger is een verplicht veld.",
+        "typeError": "Ontvanger moet een email, een gebruikersnaam of een Gradido ID zijn."
+      },
       "is-not": "Je kunt geen Gradidos aan jezelf overmaken",
       "requiredField": "{fieldName} is verplicht",
       "usernmae-regex": "De gebruikersnaam moet met een letter beginnen, waarop minimaal twee alfanumerieke tekens dienen te volgen.",
diff --git a/frontend/src/validationSchemas.js b/frontend/src/validationSchemas.js
index 53cdc6f86..a90d4556d 100644
--- a/frontend/src/validationSchemas.js
+++ b/frontend/src/validationSchemas.js
@@ -28,10 +28,21 @@ export const memo = string()
 
 export const identifier = string()
   .required('form.validation.identifier.required')
+  .test(
+    'valid-parts',
+    'form.validation.identifier.partsError',
+    (value) => (value.match(/\//g) || []).length <= 1, // allow only one or zero slash
+  )
   .test('valid-identifier', 'form.validation.identifier.typeError', (value) => {
-    const isEmail = !!EMAIL_REGEX.test(value)
-    const isUsername = !!value.match(USERNAME_REGEX)
+    let userPart = value
+    const parts = value.split('/')
+    if (parts.length === 2) {
+      userPart = parts[1]
+    }
+
+    const isEmail = !!EMAIL_REGEX.test(userPart)
+    const isUsername = !!userPart.match(USERNAME_REGEX)
     // TODO: use valibot and rules from shared
-    const isGradidoId = validateUuid(value) && versionUuid(value) === 4
+    const isGradidoId = validateUuid(userPart) && versionUuid(userPart) === 4
     return isEmail || isUsername || isGradidoId
   })
diff --git a/shared/src/const/index.ts b/shared/src/const/index.ts
index 1033ecaf1..e6fb80990 100644
--- a/shared/src/const/index.ts
+++ b/shared/src/const/index.ts
@@ -1,3 +1,4 @@
 export const DECAY_START_TIME = new Date('2021-05-13T17:46:31Z')
+export const SECONDS_PER_YEAR_GREGORIAN_CALENDER = 31556952.0
 export const LOG4JS_BASE_CATEGORY_NAME = 'shared'
 export const REDEEM_JWT_TOKEN_EXPIRATION = '10m'
\ No newline at end of file
diff --git a/shared/src/logic/decay.test.ts b/shared/src/logic/decay.test.ts
index 7678c945b..a3deedaa4 100644
--- a/shared/src/logic/decay.test.ts
+++ b/shared/src/logic/decay.test.ts
@@ -1,6 +1,6 @@
 import { Decimal } from 'decimal.js-light'
 
-import { calculateDecay, decayFormula } from './decay'
+import { calculateDecay, compoundInterest, decayFormula, decayFormulaFast } from './decay'
 
 describe('utils/decay', () => {
   describe('decayFormula', () => {
@@ -10,6 +10,18 @@ describe('utils/decay', () => {
       // TODO: toString() was required, we could not compare two decimals
       expect(decayFormula(amount, seconds).toString()).toBe('0.999999978035040489732012')
     })
+
+    it('with large values', () => {
+      const amount = new Decimal(100.0)
+      const seconds = 1209600
+      expect(decayFormula(amount, seconds).toString()).toBe('97.3781030481034505778419')
+    })
+
+    it('with one year', () => {
+      const amount = new Decimal(100.0)
+      const seconds = 31556952
+      expect(decayFormula(amount, seconds).toString()).toBe('49.99999999999999999999999')
+    })
     
     it('has correct backward calculation', () => {
       const amount = new Decimal(1.0)
@@ -26,6 +38,40 @@ describe('utils/decay', () => {
       expect(decayFormula(amount, seconds).toString()).toBe('1.0')
     })
   })
+
+  describe('decayFormulaFast', () => {
+    it('work like expected with small values', () => {
+      const amount = new Decimal(1.0)
+      const seconds = 1
+      expect(decayFormulaFast(amount, seconds).toString()).toBe('0.999999978035040489732012')
+    })
+    it('work like expected with large values', () => {
+      const amount = new Decimal(100.0)
+      const seconds = 1209600
+      expect(decayFormulaFast(amount, seconds).toString()).toBe('97.3781030481034505778419')
+    })
+    it('work like expected with one year', () => {
+      const amount = new Decimal(100.0)
+      const seconds = 31556952
+      expect(decayFormulaFast(amount, seconds).toString()).toBe('50')
+    })
+    it('work correct when calculating future decay', () => {
+      // for example on linked transaction
+      // if I have amount = 100 GDD and want to know how much GDD I must lock to able to pay
+      // decay in 14 days (1209600 seconds)
+      const amount = new Decimal(100.0)
+      const seconds = 1209600
+      expect(compoundInterest(amount, seconds).toString()).toBe('102.6924912992003635568199')
+      // if I lock 102.6924912992003635568199 GDD, I will have 99.99999999999999999999998 GDD after 14 days, not 100% but near enough
+      expect(decayFormulaFast(compoundInterest(amount, seconds), seconds).toString()).toBe('99.99999999999999999999998')
+      expect(compoundInterest(amount, seconds).toDecimalPlaces(4).toString()).toBe('102.6925')
+      // rounded to 4 decimal places it is working like a charm
+      expect(decayFormulaFast(new Decimal(
+        compoundInterest(amount, seconds).toDecimalPlaces(4)), 
+        seconds
+      ).toDecimalPlaces(4).toString()).toBe('100')
+    })
+  })
   
   it('has base 0.99999997802044727', () => {
     const now = new Date()
diff --git a/shared/src/logic/decay.ts b/shared/src/logic/decay.ts
index 35ab99803..c3b8cf3b2 100644
--- a/shared/src/logic/decay.ts
+++ b/shared/src/logic/decay.ts
@@ -1,6 +1,6 @@
 import { Decimal } from 'decimal.js-light'
 
-import { DECAY_START_TIME } from '../const'
+import { DECAY_START_TIME, SECONDS_PER_YEAR_GREGORIAN_CALENDER } from '../const'
 
 Decimal.set({
   precision: 25,
@@ -26,6 +26,13 @@ export function decayFormula(value: Decimal, seconds: number): Decimal {
   )
 }
 
+export function decayFormulaFast(value: Decimal, seconds: number): Decimal {
+  return value.mul(new Decimal(2).pow(new Decimal(-seconds).div(new Decimal(SECONDS_PER_YEAR_GREGORIAN_CALENDER))))
+}
+export function compoundInterest(value: Decimal, seconds: number): Decimal {
+  return value.mul(new Decimal(2).pow(new Decimal(seconds).div(new Decimal(SECONDS_PER_YEAR_GREGORIAN_CALENDER))))
+}
+
 export function calculateDecay(
   amount: Decimal,
   from: Date,