Can someone fix this building and breaking code?

I have a building and breaking block code for this game like Minecraft that I'm making. I click and I can get stuck in blocks. Also Sometimes when I click my Player gets deleted and I can't do anything unless I exit the game. I don't know if it's the code or something Please Help.

 var GrassBlock : Transform;
 var StoneBlock : Transform;
 var BlockSelected : float = 1;
 var Range : float = 20;
 
 function Update () 
 {
 if (Input.GetKeyDown(KeyCode.Q))
     {
         BlockSelected -= 1;    
     }
 
 if (Input.GetKeyDown(KeyCode.E))
     {
         BlockSelected += 1;    
     }
     
 if (Input.GetMouseButtonDown(0) || Input.GetMouseButtonDown(1))
     {
         var Hit : RaycastHit;
         var LookingDirection = transform.TransformDirection(Vector3.forward);
         
         if (Physics.Raycast(transform.position,LookingDirection, Hit, 20))
 {
         
         if (Input.GetMouseButtonDown(1))
         {
         
         if (BlockSelected == 1)
         {
         var GrassBlock : Transform = Instantiate(GrassBlock, Hit.collider.transform.position + Hit.normal.normalized, Quaternion.identity);
         GrassBlock.tag = "GrassBlock";
         }
         
         if (BlockSelected == 2)
         {
         var StoneBlock : Transform = Instantiate(StoneBlock, Hit.collider.transform.position + Hit.normal.normalized, Quaternion.identity);
         GrassBlock.tag = "StoneBlock";
         }
         }
     
     
     else
     {
     Destroy(Hit.transform.gameObject);
     }
 }    
 }
 }