Hey There,
i´m from Germany, so i might help you.
If you have a licence (and speak a bit german) this site is the site to go https://www.rad-net.de/modules.php?name=Ausschreibung&menuid=288&menuid=288 there you can find all road races, criteriums, time trials etc. which will happen in Germany. At some Races there will be a Category which we call “Hobby” where you can take part without a license.
Races there are mostly on small circuits, the biggest circuit i have ridden was ten kilometers in length.
If you want to do Road Races which are not Circuit races, your best bet is to look at the “German Cycling Cup” http://www.cycling-cup.de/. There the entrace fee is higher, and there are thousands of people starting. The front of the Races are pretty competitive, with teams mostly very well organized. So if you really want to race, you have to start in the first block, otherwhise its more of a Gran Fondo Style of riding. Theres even one race in Berlin.
Hope i could help you a bit!