CHECK IF THE CURRENT USER HAS SUBMITTED A GRAVITY FROM BEFORE SHOWING CONTENT. If they have hide form

Hey!
so I am trying to get my form to disappear after a user has already submitted an entry.
I found this link online that basically has the same functionality of what I want but this specific to genesis.
This is link:

I am using my own Wordpress theme. Does anyone know how I can modify this code so it works for me??

First I need it to check if user is logged in to their account, then to check if they have already submitted a post. If they have then form should dissppear. The are only allowed to submit one post at a time.

If anyone knows how to do this would be very appreciated. Thanks!