Today i had time enough to finish the installation on debian. I started the Oracle-Installer and it started as used on windows, but it got stuck when recompiling SQLNet and the Database itself. The error was "Error in invoking target..." After looking in Metalink, it seems to be a problem of a wrong compilier. After looking in the web for such problems i found the hint that the following packages have to be installed:
- autoconf
- automake
- binutils
- bzip2
- doxygen
- gcc
- less
- libc6-dev
- make
- perl-doc
- unzip
there were some packages (i did not write them down 
) that were not installed, and after retrying.... IT WORKED!
The installation finished without any problem, database started up and the Enterprise-Manager Console also worked without any problems...