diff --git a/Data/Repository/GroupRepositoryImpl.cs b/Data/Repository/GroupRepositoryImpl.cs
index 596d33d..a15ec08 100644
--- a/Data/Repository/GroupRepositoryImpl.cs
+++ b/Data/Repository/GroupRepositoryImpl.cs
@@ -8,7 +8,7 @@ using System.Threading.Tasks;
 
 namespace Demo.Data.Repository
 {
-    public class GroupRepositoryImpl
+    public class GroupRepositoryImpl:IGroupRepository
     {
         public GroupRepositoryImpl() {
 
@@ -17,6 +17,11 @@ namespace Demo.Data.Repository
         public List<GroupLocalEntity> GetAllGroups
         { get; set; }
 
+        public List<GroupLocalEntity> GetAllGroup()
+        {
+            return GetAllGroups;
+        }
+
         public GroupLocalEntity? UpdateGroupName(GroupLocalEntity groupUpdateLocalEntity) {
 
             int index = GetAllGroups.FindIndex(x => x.Id == groupUpdateLocalEntity.Id);
@@ -32,5 +37,22 @@ namespace Demo.Data.Repository
             GetAllGroups.Add(groupCreateLocalEntity);
             return groupCreateLocalEntity;
         }
+
+        public bool RemoveGroupById(int groupID)
+        {
+            GroupLocalEntity? groupLocal = GetAllGroups
+                .Where(x => x.Id == groupID).FirstOrDefault();
+            if (groupLocal == null) return false;
+
+            return GetAllGroups.Remove(groupLocal);
+        }
+
+        public GroupLocalEntity? GetGroupById(int groupID) {
+            GroupLocalEntity? groupLocal = GetAllGroups
+                    .Where(x => x.Id == groupID).FirstOrDefault();
+            if (groupLocal == null) return null;
+
+            return groupLocal;
+        }
     }
 }
diff --git a/Data/Repository/IGroupRepository.cs b/Data/Repository/IGroupRepository.cs
new file mode 100644
index 0000000..58f990b
--- /dev/null
+++ b/Data/Repository/IGroupRepository.cs
@@ -0,0 +1,18 @@
+using Demo.domain.Models;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Demo.Data.Repository
+{
+    public interface IGroupRepository
+    {
+        List<GroupLocalEntity> GetAllGroup();
+        bool RemoveGroupById(int groupID);
+        GroupLocalEntity? UpdateGroupName(GroupLocalEntity updatedGroup);
+        GroupLocalEntity? GetGroupById(int groupID);
+        GroupLocalEntity? CreateGroup(GroupLocalEntity newGroup);
+    }
+}
\ No newline at end of file
diff --git a/Data/Repository/IUserRepository.cs b/Data/Repository/IUserRepository.cs
new file mode 100644
index 0000000..e69de29
diff --git a/Data/Repository/UserRepositoryImpl.cs b/Data/Repository/UserRepositoryImpl.cs
index 5a5b9db..7b46f98 100644
--- a/Data/Repository/UserRepositoryImpl.cs
+++ b/Data/Repository/UserRepositoryImpl.cs
@@ -8,7 +8,7 @@ using System.Threading.Tasks;
 
 namespace Demo.Data.Repository
 {
-    public class UserRepositoryImpl
+    public class UserRepositoryImpl:IUserRepository
     {
         public UserRepositoryImpl() {
 
@@ -17,6 +17,11 @@ namespace Demo.Data.Repository
         public List<UserLocalEntity> GetAllUsers
         { get; set; }
 
+        public List<UserLocalEntity> GetAllUser()
+        {
+            return GetAllUsers;
+        }
+
         public bool RemoveUserByGuid(Guid userGuid)
         {
             UserLocalEntity? userLocal = GetAllUsers
diff --git a/Domain/UseCase/UserUseCase.cs b/Domain/UseCase/UserUseCase.cs
index eaa653f..89b23b7 100644
--- a/Domain/UseCase/UserUseCase.cs
+++ b/Domain/UseCase/UserUseCase.cs
@@ -10,8 +10,8 @@ namespace Demo.Domain.UseCase
 {
     public class UserUseCase
     {
-        private UserRepositoryImpl _repositoryUserImpl;
-        private GroupRepositoryImpl _repositoryGroupImpl;
+        private  readonly UserRepositoryImpl _repositoryUserImpl;
+        private  readonly GroupRepositoryImpl _repositoryGroupImpl;
 
         public UserUseCase(UserRepositoryImpl repositoryImpl, GroupRepositoryImpl repositoryGroupImpl)
         {
@@ -19,7 +19,7 @@ namespace Demo.Domain.UseCase
             _repositoryGroupImpl = repositoryGroupImpl;
         }
 
-        public List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroups
+        private List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroups
             .Select(it => new Group { Id  = it.Id, Name = it.Name}).ToList();
         public List<User> GetAllUsers() => _repositoryUserImpl.GetAllUsers
             .Join(_repositoryGroupImpl.GetAllGroups,