Germans may carry any knife other than "cutting and thrusting weapons such as daggers, swords, or stilettos", those folding knives that are locking and have a one-handed opening mechanism, or knives with fixed blades over 12.0 cm
I would suggest that Germans start carrying folding knives that have a 10-11 cm locking blade but require two hands to open. Then carry them locked open but in a sheath, concealed. That gives quick access to a legal means of self-defense. Get rid of the sheath before talking to the cops after the next "diversity" attack. If the police and government will not protect citizens, that responsibility and the associated rights fall back onto the individual.
ahhhh....that explains the meat cleaver the German fellow was carrying last week.