Hi Danylo,
this activity should be considered as self-employment and you have to pursue some steps before starting.
Please have a **** at this website: https://***.wir-gruenden-in-deutschland.de/en/recognised-refugees-with-a-permit-from-the-local-immigration-authority-auslaenderbehoerde/basic-infos/what-do-i-need/
Hope this helps a bit.
if you have any further questions don't hesitate to ask :)
Best wishes,
Anita