Need Support About Multi Session But One Client

hello, I want to make a login and admin panel page, but when I user opens the login and admin page, it works fine, but when the user opens a new tab and enters the url again, the login screen comes up from the beginning and he can log in again even though he logs in to the system, that is, double login,
my question is: how to prevent this double login? In addition, how do I start the admin panel when the user closes the page and opens it again, without having to login?

Thanks