Like my networking teacher said it last year: "You're using a Home, Kitchen and Garden-router, you won't be able to do shit with it other than using it for soccer practice".
Port forward ports 8889 and 3478 to the PC you're running TDU2 off. MAKE SURE THESE HAVE STATIC LAN IPs! (if you change locations/routers a lot, try to use MAC-based IP-allocation)
Just to make sure everything works, reboot your router and PC.
It should work.