Self-Hosted Main

Sometimes, when i do networking, i feel like im actually just stupid, and this is adjacent to my rl job so i should know this. hopefully someone here can help me.

the setup:

2 Windows PC's. one of them is used as a server for different applications. mostly games, but one of them is supposed to be ran as a fileserver now.
a tp-link router.
some netbook via wlan

essentially, i'm using the open source file browser software to host a simple browsing interface for my servers hard drive.

locally i can open it in the browser via 127.0.0.1:55537 (the port i set the application to listen to).
i can also reach the server from my main pc via its private nentwork ip 192.168.0.106:55537 (which obviously also works localy). additionally, i can reach it via radmin from an outside pc, since its a simulated network. no problems there.

additionally, i can reach it when using my routers dynamic IP address. I do not have a domain yet, but i'm planning on purchasing one once i get this working. opening it up this way, sometimes takes a very long time to respond tho, not sure why and if this is important.

anyway, I have forwarded the port with TCP and UDP in my router, which is why i can open it up by entering my routers IP.

however, i can not reach my server from a device on WAN or the internet via the routers IP or the Servers assigned IP and i have no idea why. firewalls on my router and server are disabled, so that shouldnt be it.

Anyone got some pointers for me?