How or where can I edit the related projects boxes?

[Boleyn22]

In my projects (Portfolio) I want to Show related Projects. The boxes appear and the Headlines as well, but the thumbnails all show the same Image of the current Project.
I am not able to locate the boxes. Where can I Change them and where can I Change what Projects are related, because it seems that just the newly added Projects are shown instead of those with the exact same Portfolio filter.

Ticket