Normally the use of VPN is to have local network at home (or office). There’s also a router and VPN-Server. When people are outside of home, they can use VPN-Client to connect to VPN-Server at home (or in office) and then have access to local ressources like smb shares or ssh.
So i’m using a mango router in my home network like a normal PC running wireguard vpn server and another mango router for outside my home to connect to wireguard at home. Also wireguard clients are running on iphone, ipad and notebook running linuxmint. So i can have access to my home network everyhwere i want.
So i also could use smb-share of my NAS as server over vpn and mount this smb-share. But smb is not made for internet connections and it’s quite slow, because of lots of overhead.

I don’t understand the meaning of “So it is not my case since I want the user device to access first to internet before access to GL.inet”
do you also have another internet-router?