You suggested nothing that works. When you hold it down and go to notifications it doesn't allow you to turn them off and even tho the original owner signed out and deleted this phone from his list of decices, the phone is only allowing the original owners email to be entered no other email is accepted. And I bet a million dollars that you won't resolve this issue.
Why would anybody want to help you "resolve" this issue ? If you happen to use another person's phone it's a good thing you cannot do everything with it. If you can prove it's yours bring it to Samsung, they can remove any lock and reinstall it completely.