Hmm, a few things to tackle here...

shooting someone even for a self defense is a crime
this is less gun control and more crime, but its really sad when a government puts its criminals before its law abiding citizens... Only being able to ask nicely not to have your brains blown out by a criminal with god-only-knows-what intentions really doesnt fly...

.. whats the difference? Its still a problem with the gun .. wether its about the person or controlls or gun itself .. right? x)
A better way to say it, is we dont have a gun problem, we have a crime problem. A gun is merely a tool, which can be weilded for good, or for evil. No amount of laws will affect those who by definition, have no regard for the law.

Pragmatic shooting practice is important, not only for your own safety,
Very true.
Such a shot is usually placed at the legs or arms of the target, but never in a vital area.
Very...not. You are the first person I've EVER seen claim such. Aiming at extremities puts both yourself and those around you at risk, as you are both more likely to miss (you're not clint eastwood), and less likely to disable your target. If it isn't worth killing over, its not worth DRAWING over. Guns are lethal force. If you are not prepared to kill, you should not be handling firearms in a defensive capacity. To reiterate:
If I'm in a situation where I think I should be shooting a person in the knees or arms so I don't immediately kill the person, then I'm not in a situation where I should be shooting at all.
QFE.

I'm just not comfortable with the idea that other places have, that if you simply want to own a gun, you can, and it doesn't really matter who you are.
The point is: the US have these problems exactly because just every idiot can get a firearm.
I dont understand how in USA you can get a gun just becouse its your right even if your a total psycho.
These arent really accurate. You cannot get a gun if you have a felony record. You cannot get a gun if you have a restraining order against you. Nor if you are mentally ill. Nor if you have a history of domestic violence. Indivudual states tend to vary, though these tend to hold true in most places AFAIK. Aside from the above (and maybe some things I've missed), theres no real reason to bar one from owning firearms.

Guns are a powerful tool, and they give the people who are holding them, a whole lotta power
This is a key, important statement. Guns are indeed a powerful tool. This country was founded on the notion that the power should lie with the people, and without that power, talk of free speech and religion is just talk. Sorry for invoking Godwin, but the first thing Hitler did was take the guns. I dont think I need to finish that story, we know the rest.

Even outside such worst-case doomsday scenarios, the power of the gun is highly important. The list of things a wheelchair-bound 80 year old can succesfully use to protect their home and self against a halfdozen teenage thugs is VERY short.

Yes everyone has right to defent himself- but why has to be done with guns?
Because the gun is THE best tool for the job. I am not a large person. If some 300-pound thug corners me in an alley, I'm screwed. More so if he has a knife. But if I have a gun, suddenly his size advantage is completely negated. I reemphasize the 80-year old granny from earlier in this post. If the other guy has a gun, nothing short of your own firearm even gives a chance (even then you have serious issues).

doesn't mean anything different than "don't point your gun at something you don't want to hit". It's never wise to use a gun with the intention to "kill" someone.
Not quite. It's "Don't point your gun at something you wouldn't want dead." Firearms are lethal force.

It wasn't clever in Hiroshima and it still isn't now.
Forgive the minor hyjack, and not saying I'm proud of it, but you must remember the alternative was full scale invasion of the mainland. Okinawa was considered the 'dress rehersal' for such an invasion, and it saw the bloodiest fighting of the entire war. The vast majority of troops and civilians on the island either fought to the death, or threw themselves over the cliffs to avoid capture. Upscaling that to the Japanese mainland, the leveling of two cities would have paled in comparison bloodbath that would have ensued.