How can i use touch input on android 2d game in unity?

Hello,
First i wanna say that i’m a begginer in Unity.
I want to make a 2d android game with touch inputs for the university.
I read the Unity tutorials, but i don;t understand how to script. For example, i don’t understand how to script for one touch ( when clicking the arrow for the next level) and when you take an object and move it in another place.
Thank you, and any advice is welcomed.

Script for one touch may be as below:

void Update()
{
   if (Input.touches > 0) //if any finger are on the screen 
   {
      Touch touch = Input.touches[0];
      Rect rect = new Rect(0, 0, 150, 150); //rect of your Arrow for the next level
      if (rect.Contains(touch.position))
      {
        //Do actions
      }
   }
}

Script for dragging can be looks like there:

GameObject thing;
void Update()
{
   if (Input.touches > 0) //if any finger are on the screen 
   {
      Touch touch = Input.touches[0];
      if (touch.phase == TouchPhase.Began)
      {
         Rect rect = new Rect(0, 0, 150, 150); //rect of your thing that you want to catch
         if (rect.Contains(touch.position))
         {
            thingIsCaptured = true;
         }
      }
      if (touch.phase == TouchPhase.Moved)
      {
         if (thingIsCaptured)
         { 
           thing.tranform.Translate(touch.deltaPosition);
         }
      } 
      if (touch.phase == TouchPhase.Ended)
      {
        thingIsCaptured = false;
      }
    }
}

You can learn more here: Unity - Scripting API: Input