cant log out of my phone

Check if screen time restrictions are on via screen time >content and privacy restrictions> see if allow account changes is on. If it is off, turn it on, and try to logout again

Try restarting and then try to sign out again. If you don't need your iCloud data on the phone, when signing out, if asked if you want to save the data, select no. If you choose to save the iCloud data, you will have to wait until it downloads before you can finish signing out.