Activation Lock

Start here:

https://support.apple.com/en-us/HT204306

If you have forgotten your AppleID username or password, try this - where you can recover your AppleID and/or associated password:

https://iforgot.apple.com/password/verify/appleid

One other thing...

If you don’t have access to either the original email account - or have failed to configure a “recovery” email address, then it going to get difficult.

If all else fails, you could contact Apple Support for assistance - if you are lucky, they may be able to help work through any other available options. You’ll find a link to Contact Support using the link at top-right of this page.

If you forgot your Apple ID - Apple Support

If you forgot your Apple ID password - Apple Support