Well looks like I found a solution, nothing else had worked for me.
Here my code, of course if someone uses it the functions has to be replaced.
What it does : if object clicked, marked red as long as clicked. If button is not clicked anymore, object is yellow “still selected”, if anything else is clicked than the desired object, selection is revoked.
Correct layers has to be set to objects that are clickable.
GetButton will register as true as long as the button is done. IMO the only uses for the other cases is if you want an action only ONCE on a button press (OnButtonDown) or if you want to hook into the use releasing the button. Outside of those cases I use normal GetButton for everything.