Ok, I created an account just to reply.
after reading, I noticed that the screen is still controlled by intel graphics if you didn’t set you laptop to discrete mode
I didn’t want to change, because I want to have the possibility of being hybrid.
So I found what I needed to change to be able to change the brightness.
vim /sys/class/backlight/intel_backlight/brightness
The value when screen is on maximum is 512, so 50% is 256, 25% is 128 and so on.
I’m still a noob with linux, so I still don’t know who to reroute the brightness button to change this value.
But at least now you know where to change it.