I am trying to get my enemy to follow and shoot at my fps i have a script but i am geting errors can someone help me please

 var distance;
     var target : Transform;
     var lookAtDistance = 15.0;
     var attackRange = 10.0;
     var moveSpeed = 5.0;
     var damping = 6.0;
     var Bullet : Transform;
     var Spawn : Transform;
      
     private var isItAttacking = false;
      
     function Update ()
     {
     distance = Vector3.Distance(target.position, transform.position);
      
     if(distance < lookAtDistance)
     {
     isItAttacking = false;
     renderer.material.color = Color.yellow;
     lookAt ();
     }
     if(distance > lookAtDistance)
     {
     renderer.material.color = Color.green;
     }
     if(distance < attackRange)
     {
     attack ();
     }
     if(isItAttacking)
     {
     renderer.material.color = Color.red;
     }
     }
      
      
     function lookAt ()
     {
     var rotation = Quaternion.LookRotation(target.position - transform.position);
     transform.rotation = Quaternion.Slerp(transform.rotation, rotation, Time.deltaTime * damping);
     }
      
     function attack ()
     {
     is ItAttacking = true; 
      var pel = Instantiate(Bullet, Spawn.position, Spawn.rotation);
     pel.rigidbody.AddForce(transform.forward * 8000);
     }
     transform.Translate(Vector3.forward * moveSpeed *Time.deltaTime);
     }
     
     
     }
      
      
     
      
     }