diff --git a/Demo/Domain/UseCase/GroupUseCase.cs b/Demo/Domain/UseCase/GroupUseCase.cs
index 414853a..f9e42b9 100644
--- a/Demo/Domain/UseCase/GroupUseCase.cs
+++ b/Demo/Domain/UseCase/GroupUseCase.cs
@@ -1,4 +1,6 @@
-using System;
+using Demo.Data.Repository;
+using Demo.domain.Models;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -8,5 +10,36 @@ namespace Demo.Domain.UseCase
 {
     internal class GroupUseCase
     {
+        private readonly GroupRepositoryImpl _repositoryGroupImpl;
+
+        public GroupUseCase(GroupRepositoryImpl repositoryGroupImpl)
+        {
+            _repositoryGroupImpl = repositoryGroupImpl;
+        }
+
+        // Вывести все группы
+        public List<Group> GetAllGroups()
+        {
+            return _repositoryGroupImpl.GetAllGroups().Select(it => new Group { Id = it.Id, Name = it.Name }).ToList();
+        }
+        // Создать новую группу
+        public void AddGroup(string groupName)
+        {
+            var newId = _repositoryGroupImpl.GetAllGroups().Max(g => g.Id) + 1;
+            GroupLocalEntity newGroup = new GroupLocalEntity
+            {
+                Id = newId,
+                Name = groupName
+            };
+            _repositoryGroupImpl.AddGroup(newGroup);
+        }
+
+        // Изменить название группы по ID
+        public void UpdateGroup(int groupId, string newGroupName)
+        {
+            GroupLocalEntity existingGroup = _repositoryGroupImpl.GetAllGroups().FirstOrDefault(g => g.Id == groupId);
+            existingGroup.Name = newGroupName;
+            _repositoryGroupImpl.UpdateGroup(existingGroup);
+        }
     }
 }
diff --git a/Demo/Domain/UseCase/UserUseCase.cs b/Demo/Domain/UseCase/UserUseCase.cs
index f1f44e1..544162d 100644
--- a/Demo/Domain/UseCase/UserUseCase.cs
+++ b/Demo/Domain/UseCase/UserUseCase.cs
@@ -19,28 +19,65 @@ namespace Demo.Domain.UseCase
             _repositoryGroupImpl = repositoryGroupImpl;
         }
 
-      public 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(),
-            user => user.GroupID,
-            group => group.Id,
-            (user, group) => 
-            new User { FIO = user.FIO, 
-                Guid = user.Guid, 
-                Group = new Group {Id = group.Id, Name = group.Name } }
-          ).ToList();
+        public 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(),
+              user => user.GroupID,
+              group => group.Id,
+              (user, group) =>
+              new User
+              {
+                  FIO = user.FIO,
+                  Guid = user.Guid,
+                  Group = new Group { Id = group.Id, Name = group.Name }
+              }
+            ).ToList();
 
-        public bool RemoveUserByGuid(Guid userGuid) {
-           return _repositoryUserImpl.RemoveUserByGuid(userGuid);
+        // удалить пользователя по Giud
+        public bool RemoveUserByGuid(Guid userGuid)
+        {
+            return _repositoryUserImpl.RemoveUserByGuid(userGuid);
         }
-        public User UpdateUser(User user) {
+
+
+        // Обновить пользователя по Guid
+        public User UpdateUser(User user)
+        {
             UserLocalEnity userLocalEnity = new UserLocalEnity { FIO = user.FIO, GroupID = user.Group.Id, Guid = user.Guid };
             UserLocalEnity? result = _repositoryUserImpl.UpdateUser(userLocalEnity);
-            if (result == null) throw new Exception("");
+
+            if (result == null)
+            {
+                throw new Exception("");
+            }
             Group? group = GetAllGroups().FirstOrDefault(it => it.Id == result!.GroupID);
-            if (group == null) throw new Exception("");
-            return new User { FIO = user.FIO, Guid = user.Guid,  Group = group};
+
+            if (group == null) 
+            { 
+                throw new Exception(""); 
+            }
+            return new User { FIO = user.FIO, Guid = user.Guid, Group = group };
         }
+
+        // Найти пользователя по Guid
+        public User FindUserByGuid(Guid userGuid)
+        {
+            var user = _repositoryUserImpl.GetAllUsers
+                .FirstOrDefault(u => u.Guid == userGuid);
+            if (user == null) throw new Exception("Пользователь не найден");
+
+            var group = _repositoryGroupImpl.GetAllGroups()
+                .FirstOrDefault(g => g.Id == user.GroupID);
+
+            return new User
+            {
+                FIO = user.FIO,
+                Guid = user.Guid,
+                Group = new Group { Id = group.Id, Name = group.Name }
+            };
+        }
+
+        //public List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroups().Select(it => new Group { Id = it.Id, Name = it.Name }).ToList();
     }
 }