Should I always ride on the designated bike path? I just had my first ride last week end and I generally rode pretty much in a defensive way, I always followed the cycle paths, but to be honest I enjoyed much more riding on the street for 2 reasons related to the quality and construction of cycling paths:


cycling paths outside Berlin are weirdly thought, many times they are only on one side of the road and you have to stop and cross the street to get on it, then the side changes and you have to cross again;
they are full of bumps, irregularities, debris and so on and that makes it hard to keep a decent and constant speed;


I kinda know how's the regulation in Germany, you have to be on the cycling paths only when some symbols are shown on the street.

Probably I'm not the first one to think this and I'd like to know wow do more experienced people deal with it, in the end it seems it boils down to a matter of security vs riding on a more enjoyable road.
You seem to be assuming that roads are more dangerous than bike paths. This may be true in general, but is by no means always true.

As to the legal issue, be aware of the consequences of breaking the rules. In many places (like Chile, where I am), the cycling laws simply aren't enforced. 

Beyond that, do what works for you.

So the answer to your question: No, you should not always ride on the designated bike path.