i don’t understand how i connect the pc to the domain.

Yeah, that’s the part where I think there’s some misunderstanding. You don’t “connect” the server to your domain. Instead, there is a Nameserver (most run by your registrar, GoDaddy) that hosts a list of DNS records, that you can edit, which point to IPs. If that’s set up properly and points to your public IP and the port forwarding is set up properly in the Fritz!Box you should be able to connect.

That said, what’s wrong with VPN? Particularly if you’re using Wireguard VPN, which was recently added to Fritz!Box, there shouldn’t be any performance differences. Plus, it would be safer than exposing services to the whole internet, particularly if you’re not a networking expert.