Weird characters are showing on few pages and site is not redirecting

Hello,
Since yesterday the site is acting weird , showing weird characters sometimes, cannot add anything to cart, is not redirecting to the cart, checkout not working, i even tried to restore the backup, but that didnt help at all, also deactivated all plugins but didnt help, the problem was still there.
I will be glad for any suggestions .

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