Performance issue while refresh DbContext

My WPF application work on local network, So I should update the context between machines to apply the changes over all the machine, I used RefreshMode.StoreWins as below:

             .Refresh(RefreshMode.StoreWins, _context.Appointments);

It works, but I face a performance problem, the refresh statement time increase while the appointments increase over time so it becomes so slow (Elapsed time now <1,595ms).

Do I use the correct way to refresh my context?