There is an Onroad track in Essen -
http://www.msc-essen.de/
Also in Duisburg about 20km away from essen is an Offroad Track -
http://www.rcrt-duisburg.de/
The offroad track is probably closed in the winter but maybe they have some indoor practicing in a sports hall.
For more tracks Onroad and Offroad have a look at
www.rcmap.de
Its a google based map with almost every race track in germany.
Consider yourself lucky that you are in west germany, there are the most rc tracks
