Your connection is correct (LAN to LAN), but Linksys has become an AP , not a router. You don't do any port forwarding on Linksys AP.
You only need to do port forward on UBee router to 192.168.0.15, and configure firewall on you PC so the required ports are allowed to pass.
No idea whether it's UDP or TCP ports that's required to open. I don't play games. Try either types or open both types.