how to bypass activation lock

You can't. It's a security feature that cannot be bypassed. You need the owner who's account it is locked to, to sign in and unlock it, that's the only way.

Contact the person who set the lock and have them remove it. Send them this link: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

You can't.

In that case be sure to recycle your iPhone responsibly.