Dietpi-VPN GATEWAY with Pivpn server and Pihole

Hi, I’m back on the topic after a long time, I’ll do a recap:
I have DIETPI with a PIVPN server with PIHOLE and UNBOUND;
I have a VPN with PROTONVPN provider

I would like DIETPI to act as a VPN gateway with PROTON for all my local devices (network 192.168.10.0/24)
Furthermore, I would like my SMARTPHONE with WIREGUARD that connects to the PIVPN SERVER to use PROTONVPN as a gateway
So both eth0 and wg0 must be able to have dietpi as a gateway with protonvpn.

I successfully connected with Proton through dietpi-vpn
and I ran this command:

sudo iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE

and devices on eth0 seem to have no problem dating with protonvpn.
instead the SMARTPHONE connected to PIVPN (wg0) sometimes works and sometimes doesn’t, it seems that when I disconnect it and reconnect to the VPN I can no longer access the internet or even the local devices

Maybe some iptables or routes command is missing?

Thank you