[KenWittlief]

if you want full forward to go half as fast as it is now, divide the joystick readying by two

since the center (off) reading is 128, you need to add 64 to the result to get off back to 128

joystick := (joystick / 2) + 64

if you want it even slower, divide by 4 and add 96 to get zero back to 128.

Something to consider: if your robot is way too fast with the motors running full speed, you might need to gear down your drivetrain (or use smaller wheels). This will bring down your top end, and give your robot more pushing and climbing power.