Hi, ich hab ein Problem mit den kleinen schwarzen ...

They are fungus gnats. They like wet substrate to lay eggs in. They eat dead plant material. A few is no huge issue but they can get out of hand. Yellow traps catch them, vinegar and a drop of soap in a bowl They will drown. Can neem oil the substrate to kill larva. Or look for a predatory insect to attack them.

Sticky traps will catch the adults, they're harmless, but it won't fix your "root cause" (pun intended). Soil that stays moist is prime breeding ground and the larvae CAN damage plant roots. Diatomaceous earth is a food grade product that is sharp on a microscopic level, totally safe to use, and breaks the cycle by eliminating their breeding ground. Just apply it to the top of your soil.

When I have the fungus gnats I usually water with mosquito bits. Make a tea with it. Put some sticky traps around then for the next 2 weeks bottom water and the die off. If you can't bottom water you could add soil, sand or perlite after you water to keep the top dry.

Yellow sticky pad at the soil level usually catch anything that flies.