the previous owner to my phone forgot his password what should i do?

Tell him he must go to this web site to reset his password.

https://iforgot.apple.com/password/verify/appleid#!&section=password

Once he resets the password follow the instruction on this page.

What to do before selling or giving away your iPhone, iPad, or iPod touch - Apple Support

If you are purchasing an iPhone from someone they must log out of their iCloud account on that iPhone to disable the security features. If he does not log out of his iCloud account you won't be able to setup the phone with your accounts.

If none of the suggestions Gino gave you work then ask for your money back.

my onwer move to a new place she cange her iphone and number what i post to do now if she give me her locked phone

If you cannot contact the original owner, you will not be able to activate the phone. It is worthless to you at this point. You will never be able to activate it.

If you aren't able to get assistance from the owner and are unable to get a refund for your purchase, please dispose of the device responsibly by sending it for recycling.