Setting up two Lans one with VPN and one without VPN. Having connectivity problems

I have pretty much the same problem as mentioned in this thread the thing is the solution is not really working for me because before setting things up with mwan3 or something else I need to have the VPN running.

My setup is the following I got two LANs setup by having to network bridges configured. Both bridges have two radios assigned to it and each bridge got it's own network with there own firewall zone.

Then I followed this guide of ProtonVPN to setup the OpenVPN configuration. The problem is step number 5.

At this point, the VPN is set up and your router can use it. However, the devices in the LAN of your router won’t be able to access the Internet anymore. To do this, you need to set the VPN network interface as public by assigning a VPN interface to WAN zone.

Why do my LAN devices have no more access to the internet once the VPN is configured? My plan was to configure two WAN Zones and assigning the VPN to one of them. The problem is no matter what I do once the VPN is configured, internet access is only possible via the tun0 interface.