How do I stop adding to a variable?

I think this is basic programming knowledge. Please try to learn a programming language before jumping into Unity (you can start with C/C++ since Unity uses C# and they have little difference)

Basically what you would want to do is put an if statement instead of simply increase the score. Example:

     public int score;
     public bool isAlive;
 
     void Start()
     {
         isAlive = true;
     }
 
 
     void Update()
     {
         if (isAlive)
             score++;
         else
             // ...
             // shows game over screen with max score, etc
     }