Only header & footer showing throughout site

Hi,

First of all, I am new here. A newbee on WordPress. I recently got the task to copy a company website to another domain and adjust it.
The site came with Elementor installed. I also added Polylang and Polylang Connect to Elementor.
After the copy everything worked fine. But after a couple of changes something went wrong. I was trying to find out how the templates, headers and footers work and there I changed some things, renamed some and deleted some that I thought redundant (not sure what exactly). I kept checking the results but I did not clear the cache. So when I did that suddenly I saw that all of my pages only contain a header and footer and all the rest of all the pages is gone (or at least not visable). Can someone give advice on what to do to recover the pages?

Much appreciated.

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