Hi Sefi Ninio,
There are two ways you can do it, Either change relay to SPDT Relay which is two way relay. this option is not feasible with this pcb. But if you are not using same PCB you can try SPDT relays.
Second option which can work with this setup is ,
Your light switch has two pins, connect them with gpio and 3.3 power .
when switch turn on/off gpio pin input goes high(when on) and low (when off).
You have to write a code to monitor this gpio and if its state changes, you have to toggle the relay state.
This is my idea, I havent tried it yet. and I am newbie too, Please comment.
I hope I am clear enough