[Geschlossen] Product images and thumbnails

Background of the issue:
I am trying to make product images show and appear as thumbnails on my website. The media and product are translated, but they don't seem to 'find' each other. The issue can be seen on this page: versteckter Link

Symptoms:
I expected to see images for the products, but instead, I got no image.

Questions:
Why are the product images not showing up as thumbnails?
How can I ensure that translated media and products are correctly linked?