After sleeping a night over it I did restart and came one step further. The pppoeconfig did run, but I did not get a connection. The data LED on my dsl-modem was not flashing.

Then I did reboot and tried everything, networkconfig gave with defalut values an error, but after switching to manual mode, but without changing any IP number it did work.

Pump gave an error message, but after running pppoeconfig it did work and now I am posting this using Knoppix

I will try it in a more controlled way and let you know about the results.

But anyhow this is a good community and thanks to everyone spending time to give advice.