@kalina, Thanks. So it will not work for my configuration. Wall switch (push button) is already installed. No possibilities to draw more electrical wires.
Moreover, if i put the board near the light, i have just the Neutral and the return wire from the wall switch. No Live wire to power on the mysensors board.
I think in my ase the best way is to manage everything in my garage in the electrical main board where all the wires are mapped. I can get L + N for mysensors power supply. And i can continue to reuse the original wall switch independently of the Mysensors board.
@The-Grue: Don't be embarrassed by it...pretty sure you are not the first one that fell for this trap and certainly not the last one. Hopefully also other readers on the forum can benefit from your (bad) experience in this way.
Thanks for reporting back and good to hear that some of your trust has returned towards the nrf24 and your part shops with a "good name" .