> I have tryed now for some time to NAT any port from my external / public IP
> to a server on my intra network.
> I have tryed port 80, 21, 3389 and many more. But with no luck.
You don't want to forward everything, otherwise there's no point of
having a firewall.
Use Inbound NAT, enter the external and internal port and internal IP,
and make sure you check the "auto add firewall rule".