Server fail... Only I can join

Windows 10 (newest)
FiveM (newest)
FiveM server (08-Sep-2017 19:46)


Hey there,
since a few months now me and a friend, we’re tying to set up a server. I’m the host and I set up the server like in this video: How to set up a GTA FiveM FX Server - 8/17 - YouTube
After that I portforwarded with the defaut 30120 port and with my ipv4.
(Earlier I opened the Port for my firewall but right now I can’t find where that was located…)
Well and as all this fun stuff was done I started the server like the YouTuber says… I found the server under my ipv4 and I could join. It worked perfectly fine. Then my friend wanted to join but didn’t find the server. Neither on the list, nor with direct connect, my ipv4 and the 30120 default port.
I can even put scripts in the server and these funny things and they are all working but my friend still can not join.

So my question is:
Can he not join because of my ipv4? Or can he not join because I am to stupid to set it up correctly…? It would be highly appreciated if someone could answer and help us setting up this server!

Tell him to search server name, you just join by going to search bar and searching “LocalHost”

Is the port correct? On your Port Forwarding?

Well Thats what I did and it worked so IDK.