[Koha] need help with accessing koha from outside via DynDNS

Hello, I'm still in the process of testing Koha, I have installed it on a virtual machine on my local network. This works so far. I also added some books to the database. Now I want to let other people outside of my local network test this installation, but I'm not able to reach it I can reach my network vi something.dnshome.de With a port forwarding 80 -> 80 in the network router I can reach the test page of the apache server. How can I reach the koha server -- regards Heinz