OpenWrt WLAN and LAN with VPN Tun

Hello together,

I need your help please.

I recently became aware of the OpenWRT topic and find the whole thing very appealing.

In the meantime I have reflashed my fritz!box 4040 and created a VPN tunnel.
(Why the whole thing and whether it makes sense or not is up to me. My thing)

The fritz is in the same network 192.168.50.X
The tunnel works at stations so far, so good, if I connect via gateway (OpenWRT router) and IPv6 is disabled.

My problem now is that I would like to use the whole thing over WLAN as well. However, I can't get a tunnel connection as most WLAN devices communicate directly with IPv6.
I suspect that this is the reason.

Also, my question would be if it is possible to block IPv6 somehow, so that requests going through the tunnel can't get IPv6 from my main route.

Why the same network? I want to be able to specify on each device via gateway, whether now should be communicated via tunnel or normal.

I have made some screens of the settings. I am grateful for every tip. If you find out that something else is already configured wrong, please let me know.
The OpenWrt Box gets Internet via the main router in the LAN socket.

Can no one help me here?