Weird login page after login

Hi, we have this page https://prnt.sc/FXd3Bk4_9FlY for the login screen. With this shortcode: https://prnt.sc/E_eyrapVDQyZ

But when we login and go back to the login page than the page looks weird: https://prnt.sc/sufdaThzAntT and also the menu is not working etc.

We want that people when they are logged in that they or notcan go back to login page (and redirect to another page) or something else. How can we do that?