Thanks for the link! So ich checked and it should import the "PLOAD" values from the Nastran file but it does not. I'm not sure what's the problem. 

It does import four SPC conditions from the external model but  no loads. Further it imports layers from the composite layup but there are always questionmarks next to the "Imported layers" section in the analysis tree. 

I somehow thought that it would be easier to import an entire model. Maybe somebody has an idea on what parts I should import and what should be added in ansys?