I broke my site with some code – can you help?

So I added some PHP to my site using this plugin – but I must have messed it up as the site broke. Managed to get it working again thanks to my host but this plugin is deactivated. I know if I activate it, the site will break again, but I need to activate it in order to remove the broken code, and keep the existing code that I need.

Is there any way you can help? I’m a bit lost haha.

The page I need help with: [log in to see the link]