Hello Sofian,
I am really sorry for the delay of this reply as it is a weekend for us here.
It okay
I suspected you provided that user access is not have Super admin privileges so that I can't able to access in your Joomla backend.
Is it possible assign this user account to have Super admin privileges so we can access and check on this?
Actually I have a little bit lost here, what you mean that your current user name is
sofian500, but you changed to
000sofian500 , then your site still show
sofian500, but i noticed that your user profile is showing this name now
000sofian500 , am i missing something here? Please advise.