Can't download apps, it says to sign into an email not connected to my Apple iD

If you bought a used iPhone, it was clearly not prepared for a new user properly. Who did you buy it from?

This is what should have been done on the phone before you bought it --> What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

The phone needs to be prepared correctly. Its highly likely at some point if the phone ever needs to be restored, you'll encounter Activation Lock, and without the original credentials used to set up the phone, you could be locked out permanently.

Did you recently buy this used phone? It may have been jail broken,