Sex
The Germans are as fond of sex as everyone else and remarkably tolerant of other people's foibles and peculiarities. There is great openness about sex - in-depth discussions about its problematic nature are inevitable wherever you go and any sign of embarrassment will be taken as a symptom of psychological hang-ups.
Seduction techniques leave something to be desired, and many Germans seem to rely on the age old method of boring the pants off you.
Once under way, expect full-blooded and vocal expressions of pleasure and delight (or disappointment), and don't be taken aback by frank comparisons of technique, duration, etc.
The commercial face of sex is coarse, vulgar and occasionally very strange indeed. For details, see Hamburg's Reeperbahn. In general, licensed premises and persons receive routine health inspections thus reducing the risk of contracting any unpleasant, surprises (but only slightly).
However, if you like your sex to be a mysterious smoldering ecstasy, choose the French. To the Germans it is more like an invigorating work-out in the gym or, in extreme cases, minor surgery.