I don't know what's going on there. OSM does have lots of detail for Germany and the problems with OSM are more general ones with the consistency of label placement and such. No map breaking stuff.
Apple's tiles, however have more glaring mistakes (double labels, missing labels).
It sounds like you're complaining about the quality of the OSM renderer, not the underlying data. There are a bunch of different renderers out there that can use OSM data - maybe one of the others would help?
OSM or Apple's maps? OSM has crazy amounts of accurate detail for all cities I know in Germany.
Apple's tiles have all the streets but not a lot of detail (probably by choice, nothing wrong with a sparser map, especially for the intended purpose) and the labels suck.
Apple's tiles, however have more glaring mistakes (double labels, missing labels).