Need help using one pin for two inputs

Find a small place outside of the shop about 70x70 cm, dig a hole 50cm deep, buy 2 or 3 copper rods for grounding and some thick wire, insert those rods into ground as deep as you can, connect all of them together with that thick wire and connect that wire to the grounding in the shop.
Also install one of these:
www.homemade-circuits.com/how-rccb-works-with-circuit-diagram/
www.electricaltechnology.org/2020/04/gfc...-breaker-wiring.html

Yes that will work, and it is a 30mA sensitivity, so if the grounding is done properly this will save your life in case you touch a live wire.
The functioning of it is a bit tricky as you can see the ground wire does not go anywhere near it or in it, this thing just makes sure the current flowing through any of the 3 phases and the neutral is always the same, the moment the difference between any of the phases and/or the neutral goes over 30mA or 0.03A it will trip and cut all power to everything in the house or shop.

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Personally i have those installed even on extension cables, there are at least 3 in the shop, i just do not justify not having one as it cost about 28 Euro here and it saved so many lives and so much money. Yes money, every time lighting strikes around here, one of these will trip and save everything while my neighbours end up with lots of dead equipment every Autumn.