Rotate an object in a specific time

I found that YouTube video and the rotation of the plates you can see at 15 seconds is what I want to do. https://www.youtube.com/watch?v=3JyIPCn9Nis

So here is what I'm using to rotate my plates:

 private var tCycle:float;
 var Sekundenschlaf = 2;
 var Umdrehungen = 2;
 var ZuDrehenderWinkel = 180;
 var WinkelFixierung_a = 90;
 var WinkelFixierung_b = 180;
 
 function Update(){
  var t = Time.time;
 
  if (tCycle-t<=Umdrehungen){ 
   transform.Rotate(ZuDrehenderWinkel*Time.deltaTime,0,0);
   }
 
  if (t>tCycle){
   tCycle = t+Sekundenschlaf;
   if (transform.localEulerAngles.x<WinkelFixierung_a) {
    transform.localEulerAngles.x = 0;
   } else {
    transform.localEulerAngles.x = WinkelFixierung_b;
   }
  }
 }

It's working great so far. The only problem is the speed. I can't go slower than 45 degrees. I'm really bad at math. Could you give me some tipps on how to solve this, please?