I think i bought a stolen iphone

Bummer. That's a risk you take when you buy a used iPhone from someone you don't know.

Read this --> The All Too Common SAD Reality of Buying … - Apple Community

If you can get your money back, try. If you can't, which you likely can't, then chalk this up to a bad buying decision and recycle the phone responsibly as it is totally useless to you and no one here or at Apple can help you.

Return the phone for a refund. It will be useless to you.