diff --git a/internal/contests/delivery.go b/internal/contests/delivery.go
index bbb81f3..874d361 100644
--- a/internal/contests/delivery.go
+++ b/internal/contests/delivery.go
@@ -10,4 +10,8 @@ type ContestHandlers interface {
 	CreateContest(ctx context.Context, req *contestv1.CreateContestRequest) (*contestv1.CreateContestResponse, error)
 	ReadContest(ctx context.Context, req *contestv1.ReadContestRequest) (*contestv1.ReadContestResponse, error)
 	DeleteContest(ctx context.Context, req *contestv1.DeleteContestRequest) (*emptypb.Empty, error)
+	AddTask(ctx context.Context, req *contestv1.AddTaskRequest) (*contestv1.AddTaskResponse, error)
+	DeleteTask(ctx context.Context, req *contestv1.DeleteTaskRequest) (*emptypb.Empty, error)
+	AddParticipant(ctx context.Context, req *contestv1.AddParticipantRequest) (*contestv1.AddParticipantResponse, error)
+	DeleteParticipant(ctx context.Context, req *contestv1.DeleteParticipantRequest) (*emptypb.Empty, error)
 }
diff --git a/internal/contests/delivery/grpc/handlers.go b/internal/contests/delivery/grpc/handlers.go
index 67141e4..36047a4 100644
--- a/internal/contests/delivery/grpc/handlers.go
+++ b/internal/contests/delivery/grpc/handlers.go
@@ -49,3 +49,35 @@ func (h *ContestHandlers) DeleteContest(ctx context.Context, req *contestv1.Dele
 	}
 	return &emptypb.Empty{}, nil
 }
+
+func (h *ContestHandlers) AddTask(ctx context.Context, req *contestv1.AddTaskRequest) (*contestv1.AddTaskResponse, error) {
+	id, err := h.contestUC.AddTask(ctx, req.GetContestId(), req.GetProblemId())
+	if err != nil {
+		return nil, err
+	}
+	return &contestv1.AddTaskResponse{Id: id}, nil
+}
+
+func (h *ContestHandlers) DeleteTask(ctx context.Context, req *contestv1.DeleteTaskRequest) (*emptypb.Empty, error) {
+	err := h.contestUC.DeleteTask(ctx, req.GetTaskId())
+	if err != nil {
+		return nil, err
+	}
+	return &emptypb.Empty{}, nil
+}
+
+func (h *ContestHandlers) AddParticipant(ctx context.Context, req *contestv1.AddParticipantRequest) (*contestv1.AddParticipantResponse, error) {
+	id, err := h.contestUC.AddParticipant(ctx, req.GetContestId(), req.GetUserId())
+	if err != nil {
+		return nil, err
+	}
+	return &contestv1.AddParticipantResponse{Id: id}, nil
+}
+
+func (h *ContestHandlers) DeleteParticipant(ctx context.Context, req *contestv1.DeleteParticipantRequest) (*emptypb.Empty, error) {
+	err := h.contestUC.DeleteParticipant(ctx, req.GetParticipantId())
+	if err != nil {
+		return nil, err
+	}
+	return &emptypb.Empty{}, nil
+}
diff --git a/internal/contests/pg_repository.go b/internal/contests/pg_repository.go
index 1dc1368..0443e32 100644
--- a/internal/contests/pg_repository.go
+++ b/internal/contests/pg_repository.go
@@ -9,4 +9,8 @@ type ContestRepository interface {
 	CreateContest(ctx context.Context, title string) (int32, error)
 	ReadContestById(ctx context.Context, id int32) (*models.Contest, error)
 	DeleteContest(ctx context.Context, id int32) error
+	AddTask(ctx context.Context, contestId int32, taskId int32) (int32, error)
+	DeleteTask(ctx context.Context, taskId int32) error
+	AddParticipant(ctx context.Context, contestId int32, userId int32) (int32, error)
+	DeleteParticipant(ctx context.Context, participantId int32) error
 }
diff --git a/internal/contests/repository/pg_repository.go b/internal/contests/repository/pg_repository.go
index e3f1c82..48ff720 100644
--- a/internal/contests/repository/pg_repository.go
+++ b/internal/contests/repository/pg_repository.go
@@ -68,6 +68,65 @@ func (r *ContestRepository) DeleteContest(ctx context.Context, id int32) error {
 	return nil
 }
 
+const addTaskQuery = "INSERT INTO task (problem_id, contest_id, position) VALUES (?, ?,COALESCE(SELECT MAX(position) FROM task WHERE contest_id = ? ,0) + 1) RETURNING id"
+
+func (r *ContestRepository) AddTask(ctx context.Context, contestId int32, problem_id int32) (int32, error) {
+	query := r.db.Rebind(addTaskQuery)
+	rows, err := r.db.QueryxContext(ctx, query, problem_id, contestId, contestId)
+	if err != nil {
+		return 0, handlePgErr(err)
+	}
+	defer rows.Close()
+	var id int32
+	rows.Next()
+	err = rows.Scan(&id)
+	if err != nil {
+		return 0, handlePgErr(err)
+	}
+	return id, nil
+}
+
+const deleteTaskQuery = "DELETE FROM task WHERE id=?"
+
+func (r *ContestRepository) DeleteTask(ctx context.Context, taskId int32) error {
+	query := r.db.Rebind(deleteTaskQuery)
+	_, err := r.db.ExecContext(ctx, query, taskId)
+	if err != nil {
+		return handlePgErr(err)
+	}
+	return nil
+}
+
+const addParticipantQuery = "INSERT INTO participant (user_id ,contest_id, name) VALUES (?, ?, ?) RETURNING id"
+
+func (r *ContestRepository) AddParticipant(ctx context.Context, contestId int32, userId int32) (int32, error) {
+	query := r.db.Rebind(addParticipantQuery)
+	name := ""
+	rows, err := r.db.QueryxContext(ctx, query, contestId, userId, name)
+	if err != nil {
+		return 0, handlePgErr(err)
+	}
+	defer rows.Close()
+	var id int32
+	rows.Next()
+	err = rows.Scan(&id)
+	if err != nil {
+		return 0, err
+	}
+	return id, nil
+}
+
+const deleteParticipantQuery = "DELETE FROM participant WHERE id=?"
+
+func (r *ContestRepository) DeleteParticipant(ctx context.Context, participantId int32) error {
+	query := r.db.Rebind(deleteParticipantQuery)
+	_, err := r.db.ExecContext(ctx, query, participantId)
+	if err != nil {
+		return handlePgErr(err)
+	}
+	return nil
+}
+
 func handlePgErr(err error) error {
 	var pgErr *pgconn.PgError
 	if !errors.As(err, &pgErr) {
diff --git a/internal/contests/repository/pg_repository_test.go b/internal/contests/repository/pg_repository_test.go
index beee36a..be2cccd 100644
--- a/internal/contests/repository/pg_repository_test.go
+++ b/internal/contests/repository/pg_repository_test.go
@@ -56,3 +56,99 @@ func TestContestRepository_DeleteContest(t *testing.T) {
 		require.NoError(t, err)
 	})
 }
+
+func TestContestRepository_AddTask(t *testing.T) {
+	t.Parallel()
+
+	db, mock, err := sqlmock.New(sqlmock.QueryMatcherOption(sqlmock.QueryMatcherEqual))
+	require.NoError(t, err)
+	defer db.Close()
+
+	sqlxDB := sqlx.NewDb(db, "sqlmock")
+	defer sqlxDB.Close()
+
+	contestRepo := NewContestRepository(sqlxDB, zap.NewNop())
+
+	t.Run("valid task additional", func(t *testing.T) {
+		taskId := int32(1)
+		contestId := int32(1)
+
+		rows := sqlmock.NewRows([]string{"id"}).AddRow(1)
+
+		mock.ExpectQuery(sqlxDB.Rebind(addTaskQuery)).WithArgs(taskId, contestId, contestId).WillReturnRows(rows)
+
+		id, err := contestRepo.AddTask(context.Background(), contestId, taskId)
+
+		require.NoError(t, err)
+		require.Equal(t, int32(1), id)
+
+	})
+}
+
+func TestContestRepository_DeleteTask(t *testing.T) {
+	t.Parallel()
+	db, mock, err := sqlmock.New(sqlmock.QueryMatcherOption(sqlmock.QueryMatcherEqual))
+	require.NoError(t, err)
+	defer db.Close()
+
+	sqlxDB := sqlx.NewDb(db, "sqlmock")
+	defer sqlxDB.Close()
+	contestRepo := NewContestRepository(sqlxDB, zap.NewNop())
+	t.Run("valid task deletion", func(t *testing.T) {
+		id := int32(1)
+		rows := sqlmock.NewResult(1, 1)
+
+		mock.ExpectExec(sqlxDB.Rebind(deleteTaskQuery)).WithArgs(id).WillReturnResult(rows)
+
+		err = contestRepo.DeleteTask(context.Background(), id)
+		require.NoError(t, err)
+	})
+}
+
+func TestContestRepository_AddParticipant(t *testing.T) {
+	t.Parallel()
+	db, mock, err := sqlmock.New(sqlmock.QueryMatcherOption(sqlmock.QueryMatcherEqual))
+	require.NoError(t, err)
+	defer db.Close()
+
+	sqlxDB := sqlx.NewDb(db, "sqlmock")
+	defer sqlxDB.Close()
+	contestRepo := NewContestRepository(sqlxDB, zap.NewNop())
+
+	t.Run("valid participant addition", func(t *testing.T) {
+		contestId := int32(1)
+		userId := int32(1)
+		name := ""
+
+		rows := sqlmock.NewRows([]string{"id"}).AddRow(1)
+
+		mock.ExpectQuery(sqlxDB.Rebind(addParticipantQuery)).WithArgs(contestId, userId, name).WillReturnRows(rows)
+
+		id, err := contestRepo.AddParticipant(context.Background(), contestId, userId)
+
+		require.NoError(t, err)
+		require.Equal(t, int32(1), id)
+	})
+}
+
+func TestContestRepository_DeleteParticipant(t *testing.T) {
+	t.Parallel()
+	db, mock, err := sqlmock.New(sqlmock.QueryMatcherOption(sqlmock.QueryMatcherEqual))
+	require.NoError(t, err)
+	defer db.Close()
+
+	sqlxDB := sqlx.NewDb(db, "sqlmock")
+	defer sqlxDB.Close()
+
+	contestRepo := NewContestRepository(sqlxDB, zap.NewNop())
+
+	t.Run("valid participant deletion", func(t *testing.T) {
+		id := int32(1)
+		rows := sqlmock.NewResult(1, 1)
+
+		mock.ExpectExec(sqlxDB.Rebind(deleteParticipantQuery)).WithArgs(id).WillReturnResult(rows)
+
+		err = contestRepo.DeleteParticipant(context.Background(), id)
+		require.NoError(t, err)
+	})
+}
diff --git a/internal/contests/usecase.go b/internal/contests/usecase.go
index c076721..7892518 100644
--- a/internal/contests/usecase.go
+++ b/internal/contests/usecase.go
@@ -9,4 +9,8 @@ type ContestUseCase interface {
 	CreateContest(ctx context.Context, title string) (int32, error)
 	ReadContestById(ctx context.Context, id int32) (*models.Contest, error)
 	DeleteContest(ctx context.Context, id int32) error
+	AddTask(ctx context.Context, contestId int32, taskId int32) (int32, error)
+	DeleteTask(ctx context.Context, taskId int32) error
+	AddParticipant(ctx context.Context, contestId int32, userId int32) (int32, error)
+	DeleteParticipant(ctx context.Context, participantId int32) error
 }
diff --git a/internal/contests/usecase/usecase.go b/internal/contests/usecase/usecase.go
index 5437e17..633bab3 100644
--- a/internal/contests/usecase/usecase.go
+++ b/internal/contests/usecase/usecase.go
@@ -29,3 +29,19 @@ func (uc *ContestUseCase) ReadContestById(ctx context.Context, id int32) (*model
 func (uc *ContestUseCase) DeleteContest(ctx context.Context, id int32) error {
 	return uc.contestRepo.DeleteContest(ctx, id)
 }
+
+func (uc *ContestUseCase) AddTask(ctx context.Context, contestId int32, taskId int32) (id int32, err error) {
+	return uc.contestRepo.AddTask(ctx, contestId, taskId)
+}
+
+func (uc *ContestUseCase) DeleteTask(ctx context.Context, taskId int32) error {
+	return uc.contestRepo.DeleteTask(ctx, taskId)
+}
+
+func (uc *ContestUseCase) AddParticipant(ctx context.Context, contestId int32, userId int32) (id int32, err error) {
+	return uc.contestRepo.AddParticipant(ctx, contestId, userId)
+}
+
+func (uc *ContestUseCase) DeleteParticipant(ctx context.Context, participantId int32) error {
+	return uc.contestRepo.DeleteParticipant(ctx, participantId)
+}