OpenVPN as separate network interface

Hey all,
currently I'm trying to get an OpenVPN configuration working for my setup.
My provider gave me a .ovpn file, so that I can access the VPN by running:

sudo openvpn -config /etc/openvpn/Config.ovpn

But after the command is executed the web interface is not reachable (I can access by IP, but I want to do it by Domain).
Furthermore Plex and Nextcloud are not working too.

I thought about it and I think that the VPN connection is blocking my eth0 network card.
So I try to get a solution that does something similar to a Windows system.
If I install a VPN Tool, I get a new network adapter which runs in parallel.

If my browser or application uses my "normal" network card, I am still in the un-tunneled network.
Otherwise the new network adapter sends all request trough the VPN tunnel.

Is there a way to tell my download-applications to use a new vpn network interface so that my other services are still working?

With best regards
LouBen3010

Thanks for your answer!!
It looks very complicated..

If someone did this before with an OMV system I think a little guide will be helpful.
Otherwise I need to cancel my VPN subscription or need to download my stuff manually on windows and put it onto my server.

Have a nice day!