As a result to the first replies, I changed the title of this post…
I had been through the guides that you have linked me to before I made this post in the first place, so unfortunately they did not help.
I have tried forwarding different ports, but the connection is still listed as Relayed. I have forwarded other ports as well for different apps, and they work fine, so the forwarding is done correctly.
I should be able to access the server from Filezilla, though, but I haven’t had any luck so far.