As I suspected the DNS is not setup correctly. the domainname and all it's subdomains point to the external IP address of an ADSL connection.
The used 192.168 range in ISPConfig is for internal LAN usage and should not be exposed on the internet.
Being behind an ADSL router, I suggest to forward on your router the ports 80 (www), 25 (mail) and 21 (ftp) to the server. How to do that is dependent on your ADSL modem. Be aware, that sending emails directly from your server (after you get it up/running) is like sending from a dynamic IP, which many receivers don't like and in fact block. Consider to setup a mail relay solution.
After forwarding port 80, www.domain.tld
should show you a site. Beware, that this is the only site you can have. I'm not sure but IIRC ISPConfig needs to have the external IP address configured (not your server!).