Home folder named Guest and not main users name

If you unlock the padlock at the bottom left of the Users & Groups screen then right click on your account and select advanced, you will get this screen.

You will see that the account name is guest and the "full name" is Big Al. You can make the full name whatever you want and it does not impact the account name. Whenever you first setup the account you apparently picked guest as the account name. It is not really hurting anything and you can just leave it alone.

If you want to change it, follow the steps in this document. Make sure you backup first. One wrong move in that screen and you can lock yourself out of the account.