Logging out old appleid

A friend gave me an IPhone 7 but he didn’t log out his appleid from the phone/iCloud. I have tried to log in my is but it keeps asking for his password to log him out and to reset all the settings and log-ins. How do I remove his is/data from the phone and log in my appleid. Btw, I can not reach him to just get his info so what do I do?