I have a question about the Xbox (Upnp) not required?

I'm at Telekom and I once googled you shouldn't actually do it that you go free UPnP for the hackers and that's why I ask you what I can do

In routers from us there's no possibility to release UPnP flat rate. But you can open special ports in the rule settings.

But it is important to note what you are opening. As you have already written correctly, open ports are always vulnerable. So you should know what you're doing there.