Hi all thanks for the replies,
The joystick is a cheap aliexpress one, just try everything and to keep the cost down, the reason why i wanted one with potentiometers, is that i can adjust the sensitivity of the joystick through the arduino. (link: https://nl.aliexpress.com/item/1PC-New-Arrival-4-Axis-Plastic-For-Joystick-Potentiometer-for-JH-D400X-R4-10K-4D-with/32828346645.html?spm=a2g0s.9042311.0.0.9nbO48)
If been searching a bunch and came to the conclusion i needed solid state relays after the arduino for the valves to be operated.
And found that step down converters can be used to lower the voltage: Also read a bunch about step down converters for the 12 volt signal from the button, https://nl.aliexpress.com/item/DC-CC-Max-9A-300-W-XL4016-Step-Down-Buck-Converter-5-40-V-om-1/32845724444.html?spm=a2g0s.9042311.0.0.LQk0aH
The housing, thinking of repurposing my old lunchbox as arduino and relay housing :), will be in the tractor itself, while using it and when in 'storage' i might make it disconnectable via plugs as dust will be an issue in the storage.
When switching when you pressed the button i want it to stop the valve, basically stop the signal.