THANK YOU !!! They all at DAZ told me, that I was doing something wrong with my folder organization, but N.O.B.A.D.Y. was willing to tellme, how it is done correctley. DAZ Studio might be great, but their support is ****.

EDIT: Tried to solve my problem by reorginazing my folder structure. Didn't work. There seem to be a stereotype answer from the DAZ-support, whenever you having issues with DAZStudio: "Oh, you've got nested library - end off".