I have my VPN up now. All running and can check connectivity with IPLeak or in system logs. However, when I run my phone and the VPN client over the Vodafone connection I get 40MBPS. When I run anything over the OpenWRT client connection I am getting 0.1-0.2Mbps....
Which VPN endpoint (location of server) are you using?
Try a server in the UK to see if there is an improvement in speed.
Get a free account from ProtonVPN and try speedtest with one of the free servers to see if speeds are any better.
https://openwrt.org/docs/guide-user/services/vpn/openvpn/performance