It's a bit hard to make out in the photo, but there the center is a larger black insect being swarmed by dozens of small light brown ones. The larger one looks like some sort of beetle. What are the smaller ones?
It's probably beetle mites, see German Wikipedia article for a post cture similar to yours, unfortunately the English contains only a close up.
Here a translation by DeepL of the introduction and the section on its way of life:
The common beetle mite (Parasitus coleoptratorum) is a species of mite that is often found as an ectoparasite on beetles.
The species lives on the dung of large mammals, for example horse dung, where it feeds predatorily on threadworms and other tiny creatures such as fungi. If the dung dries out, the deutonymphs mount dung beetles en masse and allow themselves to be carried to a new substrate. Only when this is fresh do they descend and develop into adults, which only live for 6-10 days. Oviposition takes place on the hosts. The species is fully grown after three moults.