Next time, please use the # image to embed your output in CODE tags. makes it much more readable.
Means you want to access your panel from the outside?
content of /etc/hosts:
root@server1:/home/mariou/install_ispconfig# cat /etc/hosts
127.0.0.1 localhost.localdomain localhost
192.168.100.1 server1.example.com server1
Means you have your server behind an ADSL router, right?
So you need to make sure www.xyz.de
forwards/points to your external IP address used for your ADSL connection.
Next you need to forward port 81 on your router to the server you have with ISPConfig.