I studied law in germany for a couple of semesters and I learned that human rights are never absolute. They are more like bubbles. Basically your right ends where it collides with someones else right or to paraphrase it "one man's freedom is another man's limitation".
The purpose of the law is to make sure, that those bubbles are about equally sized for everyone.
0 would be equal size for everyone, so I would hope the purpose of the law is more than that. I wouldn't also take Germany as particularly good example because, for example, free speech is not a right in Germany (they may claim they have very good reason for that, but don't they always do so?).
Rights are "not absolute" only is the sense that exercising your right does not absolve you from responsibility for violating other people's rights. So, if you exercise your right to freely use your property, say, a gun, and shoot somebody - you'll go to jail. But not for using your gun - but rather for violating other's right to live unshot by your gun. Your right to use your property didn't go anywhere, but it also didn't remove your responsibility for the consequences of such use. If there's no consequences, there's no place for government to intervene (I know most governments disagree, of course they do).
You completely skipped over: your right ends where it collides with someones else right
This seems to be the most natural definition of rights. I can say whatever unless doing so prevents you from also speaking. Thus, I can't use even larger speakers to drown out what a protesters outside my factory are saying. But, I could use them to convey my message.
Where did you get the idea that "free speech is not a right in Germany"? Free speech _is_ a right[1]. But, following the principle outlined by Riesling it is not an absolute right.
In Germany, speech that is deemed to "incite hatred" is illegal, for example. Also, denying or approving certain things publicly is illegal, even if this deed leads to no harm to anybody.
That means no freedom of speech. Freedom of speech includes freedom of saying false, hateful, disturbing and insulting things too. "Not absolute right" means not freedom but government-approved limits. That's exactly what my point was - when you move from protecting rights to banning stuff that does not violate anybody's rights but is unpleasant for people to witness and so banning it is popular - you have a problem with freedom.
Don't feel too bad for Germany though - most countries have problems with freedom of speech. It's a hard concept to maintain, since it is unpopular and disturbing speech that needs protecting - nobody objects to popular or neutral speech.
The purpose of the law is to make sure, that those bubbles are about equally sized for everyone.