"Once you manage to enter the cell phone screen"
If you've properly secured your smartphone , it's gonna be difficult to even access the phone's features.
Ours require a password to unlock, and you're NEVER gonna guess passwords we use, and which we change once a month
Not sure where you're getting at?
If you registered your phone number to recover your email password. The malicious person only has one security barrier to break through unlocking your cell phone. Once inside the cell phone, it can ask to reset the password of any known e-mail and enter bank accounts, websites, etc... It can add a digital and easily access any app that uses a registered digital. The two-layer factor won't help at this point. The individual will already have your phone and e-mails.