You were right! There were problems with ghostscript.
I fixed this. I also had to remove the ssl-cert dependency
from the server, because it was not possible for me to let
it configure correctly. But I uploaded ssl-cert. Maybe someone
can find the problem. It failes with the creation of ssl-cert-snakeoil.pem.

I could watch, that the internet connection is established very often.
I don't know, if it was before installing cups-client.