Q: can only log in as guest user

Hey there Ruth,

Welcome to Apple Support Communities.

From what I gather, there's an issue logging into a user account on your MacBook Pro. If the issue is related to the password for the user account, use article below to resetting the account password.

Change or reset a user account password on your Mac - Apple Support

If you know the password and the issue only occurs in a specific user account, take a look at this article and try starting up your Mac in safe mode:

Try safe mode if your Mac doesn't finish starting up - Apple Support

So long.