update_user_meta updates to a wrong ID

That’s likely because you are using $current_user->ID, which always refers to the currently logged in user, or when “empty” object if not logged in (ID == 0). If you would like to update user meta on any other user you would have to supply the user ID of that user in the $_POST data as well.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)