The aren't able to infiltrate left groups.

They never were and never will be. Most of German cops are rather 'dim' and hence rather lean to authoritan ideologies. To not euphemise too hard.

Nazis on the other hand: Most of these guys shine exactly in their brightness.

The infamous NSU trio got all of its weapons from police "double"-agents. ("V-Leute").

German police is chronically blind on its right eye, so to say. We also got Nazis in the police force stalking their ex-girlfriends, e.g.

And whenever they shoot or hurt an illegal or migrant citizen here or there, it is just bad luck. Like 200 times a year, on average.

There even was a muslim man that literally burned to death in his cell. "Unexplainably" by some magic coincidence. In 2006 if I remember correctly.

Also you got Nazis shooting politicians quite regularly in Germany.

I'd advise strongly against wearing a Kippa when visiting Berlin or Eastern Germany in general. Western Germany hasn't so many Nazis. There we have migrant cartel's ("Clans") ruling the bigger cities instead.