Aussiedlers in Dusseldorf, Hamburg, Cologne and other majority cities. Aussiedlers are of german descent that grew up in Soviet Union, they are part of the Russian OC, but slightly different.
Dusseldorf is the capital of OC in Germany, everyone has something going on in the city. Aussiedler, Russian OC, Albanians, Ndrangheta in narcotics mainly Cocaine, Camorra mainly construction, La Cosa Nostra they have been quite for over a decade but still there, Balkans different nationalities are often violent and do jobs for other OC groups or work for them. Turks have a large presence in the city but I have been told they seem to have decreased in membership and activities this past decade, Yakuza like the Turks have decreased in both but have gone more white collar, Greeks mainly smuggling and fraud, but like the Turkish and Yakuza have also decreased. There are also traveling crime groups that visits that city.

On the town outside Frankfurt, until more details arrive, I suspect the Serbians or Moroccans, those two are major groups in the area and have been known to be violent for half a decade.