rotation using the left arrow of the keyboard

i have a script(not written by me) to move a character forward(right arrow) and backward(left arrow) with the jump action(up arrow)...but i need my character to rotate when i press the left arrow and to also use the back arrow to move when rotated...i need answers pls...

 var speed : float = 6.0;
     var speed2 : float=10;
     var jumpSpeed : float = 8.0;
     var jumpSpeed2 : float = 18.0;
     var gravity : float = 20.0;
     private var moveDirection : Vector3 = Vector3.zero;
     var pop : AudioClip;
   //  var puzzle : AudioClip;
   
     
     function Update() {
    if(Input.GetKeyDown(KeyCode.RightArrow)){
     animation.Play("TIMI ANIMATION");
     //audio.PlayOneShot(puzzle);
    }
     
     if(Input.GetKeyDown(KeyCode.LeftArrow)){
     transform.Rotate(Vector3(0.0, 180.0, 0.0));
        } 
 
  var controller : CharacterController = GetComponent(CharacterController);
         if (controller.isGrounded) {
             // We are grounded, so recalculate
             // move direction directly from axes
             moveDirection = Vector3(0, 0, Input.GetAxis("Horizontal"));
             moveDirection = transform.TransformDirection(moveDirection);
             moveDirection *= speed;
             //audio.PlayOneShot(puzzle);
             
            if(Input.GetKey(KeyCode.UpArrow)){
                 moveDirection.y = jumpSpeed;
                 audio.PlayOneShot(pop);
             }
         }
         // Apply gravity
         moveDirection.y -= gravity * Time.deltaTime;
         
         // Move the controller
         controller.Move(moveDirection * Time.deltaTime);
     }
     function HighJump(){
      var controller : CharacterController = GetComponent(CharacterController);
        /*  moveDirection = Vector3(0, 0,
                                     1);
             moveDirection = transform.TransformDirection(moveDirection);
             moveDirection *= speed2;
             */
            
                 moveDirection.y = jumpSpeed2;
             
         
         // Apply gravity
         moveDirection.y -= gravity * Time.deltaTime;
         
         // Move the controller
         controller.Move(moveDirection * Time.deltaTime); 
      }