After password reset not able to login the laptop Access denied error

I bought a 2nd hand notebook for my sister. Wanted to change settings, “no password login screen” and “change power options”. I could change that but the login screen kept coming.

I had the idea that another account was overruling. so I did net user administrator / active: yes. then I saw 2 accounts “admin” and “mine”. I could not change the type from the first one, so I changed mine to standard.

active: no and restarted, login screen still came and ones logged in I could not do any setting everything “ACCESS DENIED” if ask for "you want to make changement? there is no YES button, run as administrator = access denied.

When I restart I see 2 accounts “DELL” and “mine” no matter what I choose it opens my account. Ones I could change from my Microsoft account to a local account. I did not need to put a password to login but the desktop was the same and also denied everything
Netflix denied put users into the administrator group denied …

Any Suggestion,?