Critical Error PHP

Hello,
I am writing to you in regards to site samuelblack.co that I am helping my husband fix.

I have my own site rosenreckless.com where I use Enfold theme that I purchased and installed myself and that is the license number I was using for being able to log in a kris.

However, for samuelblack.co it was his old intern that purchased and installed Enfold theme (child) for the site back in 2015 and I do not have license number etc.

Until recently I was getting a critical error but at least I was able to log in to wp-admin or wp-login, now I can’t even log in to the wp-admin or wp-login.
I contacted our hosting company and they said that all the errors that I’m getting are with the theme and php configurations/critical/core files of the theme.

I was hoping you’d be able to help me out. I am not even sure where to begin.
Thank you
Ksenia