Who told you that? Of course you have the right to defend yourself - even with deadly force (§ 32 StGB Notwehr). If my or another´s life is at risk, I may kill the attacker. It´s just that we´ve gun control.
The killing of the six people at the restaurant is sad. The picture with the article shows the good side of Germany. A nicely painted building, the clean cobbled street and walk and no news TV truck parked at the curb blasting the tragedy up to a satellite for distribution.
That's laughable.
I have Springfield 45, my wife a Kimber 45 (For concealed carry). I can carry that weapon concealed nearly anywhere I go (With few exceptions). In Texas in 2006 alone over 62,290 got their concealed handgun licence and they did so fairly easily. These are not special officers of the state, they are people like you and I. You have a right to defend yourself, but you lack the means, and the state (Staat) reserves this right only to itself. If "you" as a law abiding citizen, someone trained in their use, were to carry a concealed weapon what would happen to you if caught?
http://www.49abcnews.com/news/2007/jan/22/concealed_carry_permit_holder_shoots_suspect/
http://www.charlotte.com/mld/charlotte/16558610.htm
If you're threatened what are you going to do? Scream, "Stop, ich habe ein Buttermesser!" Defacto you have no right to self defense because the means of self defense are denied.
Even the right to own a gun all together is made excruciatingly painful and this is done intentionally to discourage gun ownership. I had a few guns while in Germany and it does cost a lot of money, there are a lot of restrictions, they require licensing, club membership, bla bla bla, which in all reality amount to the state squeezing a lot money out of people and making it intentionally difficult. It's a bureaucratic hurdle intended to make people fail. There is a difference between a right and a privilege. If the state can deny you ownership though you are a law abiding citizen, it's a privilege, not a right to own a gun in Germany! If you lack the means to self defense and the state (Staat) reserves this right for itself, which is the case in Germany, you defacto have no right to self defense. Call the Polizei or hope the BVS does their job, but "you" as a citizen lack the means.