Please note that Germany has (compared to other EU members) quite strict and company-friendly protesting laws.
Such protests may be even considered as political protest (Politischer Streik) which makes them not illegal per se but could be illegal. https://www.bpb.de/themen/medien-journalismus/netzdebatte/219308/ein-bisschen-verboten-politischer-streik/
As always with conservatives: