Countdown don't worke.

I cant understand how split this timer (Countdowntimer) .
I want make a 2 Min Countdown, an Button with start funktion and an Score.
Start Button (visible) --> click on Button --> countdown start (in this Time is the Start Button grey"cant click funktion") --> Add 1 Point to Score.

I would be very happy if someone could help me with the code. have been sitting for days.