I finally resolved the issue with my bandwith.
It was frustrating issues stacked on top of each other. Here the things I had to do :
1. Install a GB internet card in ZS server
2. Set the ling to 1GB on the fritzbox with that the bandwith did go from 10 to 18 down
3. on the fritzbox disable ipv6 the bandwith did go all the way to my max of 30
4 Take the server downstairs and connect no connection, it worked with the 100mb card. Apparently the cable in the wall or one of the connectors has an issue
5. use an alternate cable from the wall.
YES full speed internet both ways. It is done and it was not Zeroshells fault.
I am very glad it works now. the next FW server will be a tiny box next to the router to exclude these other issues.
Fulvio keep up the great work. I love your product