yes, as already mentioned, there is a drawback: your teammate needs to create a VPN connection in Windows or install OpenVPN (and you then have to send them the connection file). Hamachi has advantages in this regard...

The most important thing: I have the same router, and I spent a week figuring out "why can't I play Heroes?"... Set up port forwarding for Heroes on your router (to the IP address of the computer that will be the server)... And...
Disable the UPnP function on the router's internet settings page. You won't be able to play without it (don't forget to restart the router afterward).