Thanks a lot my friends
Most of the base is made of a special kind of wooden plates. Here in Germany we call it "MDF" the means "
Mittel
dichte
Faserplatte" -> "Medium-density fiberboard".
I think there will be similar products in the us. The plates can be processed very well but they can be painted very badly. Therefore, I have covered all the pieces of wood with polystyrene plates.
Also the "detials" were made of small polystyrene pieces.
The black floor is also a MDF-plate, foiled with glossy black car wrapping foil
This is much earier than painting.
Here are some "making of" pictures.
I hope this "helps" a bit - and sorry for my terrible english....