My first image on homepage doesn’t link to corresponding post

Since installing my website back in February 2020, I have had this problem.
I have always had to manually add the post’s link to the first image of the post – but that is an endless loop, because as soon as one does open the post, the image “lights” up when scrolling over it, of course then leading to the post again and again.

Where is the function to make all first images of any post lead to the post itself? Without adding link manually?

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