thursday games (when announced in the forum) and friday games are open house, we only ask that you announce yourself in the respective thread so we have an idea of how many people there will be
as for “normal” groups, as healywp already said, casting a wide net is an option, if you want to play in german there is Athenaes Siegel (info can be found in this post)
Besides that i recommend just coming to a couple of the open games so people can get to know you, we definitly spawned more than one campaign and quite a lot of new DMs with those 