So far it seems like everythings working. Network and harddisk were found and the installer is just preparing it for an encrypted LVM, so Im pretty confident everything will work out alright.
After some troubles, he got there:
After spending two days in frustraion I finally managed to get the Debian Netinstall working from a USB pendrive. I actually wasted a lot of time with my corrupted MBR, so the crucial part that helped me was issuing the comand lilo -M /dev/sda on the machine I was preparing the pendrive on.