I need help on setting up my port forwarding I think because I can only join my server and not my friends.
You have to open your port (30814 by default) on your internet connection. It depends on the internet provider you have. I don’t know where you come from but in France, you have to open the web interface of your router and go to NAT/PAT and add the necessary port with the LAN IP of your PC (computer). If you have the possibility to access the web interface of your box (router), look at the interface for network properties.
For more informations : Server | BeamMP