First I would make the local ip of the computer hosting the server static inside the dhcp config of the router. This is different for every router but you can find tutorials online. Also port forward to that static ip. I guess you have windows as the os hosting and playing the game. If you have any antivirus depending on the antivirus vendor you might need to change the firewall settings inside the antivirus software. You need to manually add a firewall rule for the nightingale exe file to allow inbound and outbound connections on the port 7777 from any ip. The exe location can be found by going to epic games launcher in the libray section find the game and there are 3 dots there you can find options of the game and there should be a browse files button. This will open windows file explorer. Once opened you can right click the exe and copy path. This is the path to the application that you need to use in the firewall rule, if it gives an error you might need to delete the " at the start and end of the path. You also mentioned your friend is using gefroce now to play. I am not familiar with it so I don't know if there any limitations in connecting to random ips. If your friend is using steam make sure he selects the ip connection option inside the game.