Okay, first off, that law isn't passed yet and more often than not such laws get shot down by the Bundesrat. So let's wait a while.
I don't think this law will be passed.
There were similar populist propositions when Erfurt happened concerning videogames that didn't pass, either.
Also, violent videogames are not banned, they just cannot be sold to people under the age of 18 and no advertising is allowed for them. The censorship is much worse than the so-called "banning" but it's still legal to get UK/US imports when you're older than 18 which is what I usually do. So no real problem there, either.
Third: Gun-posession is only allowed for certain people, such as police officers, soldiers, watchmen, hunters, people who use them recreationally in a gun club...
And lastly, the biometric authentification is a really good idea. Might help to avoid a stupid kid just taking his father's gun out of the nightstand...
Don't overreact, people...