Minecraft Java Paper Server Help

[Greninji88]

I want to make a Minecraft Java server, with Paper MC for plugins. I successfully did that, it stats up and people on the network can connect. however, I tried port forwarding (GL.inet Travel Router) and when others outside of my network attempt to connect, they are given the error: "Connection timed out, getsockopt".

I allowed it through firewall, but maybe I'm doing something wrong. If you can help me that would be appreciated, I also need clarification on the whole port forwarding thing, as I don't know a lot about how to set it up with IP and ports, etc. Thank you