How do i create mobile menus

I CAN’T FIND ANYTHING!!!

Is there something like “Input.GetMouseButtonDown(0)” but for ios/android?

Yes - Input.GetMouseButtonDown(0) works on IOS and Android.

On mobile platforms touch is simulated as a mouse input.

You can also use Input.touches to work through each touch and check for the phase (Began, Cancelled, Move, Stationery etc).