Was sind das und wie behandle ich sie?

There are treatments you can buy at the store/online. Many use water with a little dishsoap (it suffocates them).

As the other poster mentioned, gardenhose is the fastest way to get them all off. Unfortunately they will keep coming back, so make sure to be dilligent in checking every 1-2 days and repeat whichever method you use. Hand-picking also works for small plants in pots (doesn’t look like that is the case here) – they squish very easily.

(Whichever water-based treatment you use, try to avoid doing it mid-day when the sun is up, you may burn the plant and cause even more harm).

Fun fact: Aphids are born pregnant! (so they spread quickly)

Neem oil kills them instantly

It’s aphids, spray them off with a water jet from the hose.