I found out by reading in the forum that freewebs only listens to the url and not to the IP. So If I want to host more than on Webapp I have to add a virtual network and bridge it to my physical. Then I have to add this to a DNS and add a new webapp to Freewebs.
If I want to make this Webapp available from the internet I also have to give an extra IP and add this to the external DNS.
Or is there an other way to make this Webapp available by using my main-url with a different port and redirect it with the router to the IP of the secound Webapp.
I think it´s not possible, but maybe.