Login Issue

I’m helping a friend who registered a ww.wp.xz.cn website with the help of someone and then didn’t work on it until after all the passwords were changed. The site URL displays the site. We’ve determined the username but don’t have the correct email address or password to access the admin screens to update/post etc. The email password function isn’t working as it seems like an unknown email address is registered to the account. How do we proceed from here to determine the password and email address and get into the account?

Any help in this regard would be much appreciated.

Linda