You should check to see if your router has UPnP abilities. Log into it & check your Firewall status. I suspect UPnP is listed there. Make sure it's enabled.
The log-in address should be 192.168.1.254 with admin as both name & password.

You 'might' need to port forward the device. If so, you need to do this first: Set up a Static ip Address: Setting up a static ip address
This above step must be done first.

Then follow these directions: Port Forwarding Limewire on the Siemens Gigaset SE567

I'd suggest you give LW a wide-ish port range.

Oh .. the LW sample image they use is for LW 4, for LW 5 see Manual port forward instructions & sample image