Smooth swapping my game object

In my game i want to move my player to x-direction using swapping (3-position -9,0,9 ), I wrote the programme but smoothing was not good i try with Vector3.lerp but my object move smoothly but when i give speed to player move zig-zag pattern (player move second lane little back and go initial position. I write down program plz help about this. using UnityEngine; using System.Collections;

public class playercontrol : MonoBehaviour {

 Vector2 firstPressPos;
 Vector2 secondPressPos;
 Vector2 currentSwipe;
  Vector3 spos,endpos;
 public    bool check = false  ;

public float time = 0; private float movetime; private float moveduration=0.1f; void Update() { playera.transform .Translate ((Vector3.forward speed Time.deltaTime));

     if(Input.GetMouseButtonDown(0))
     {
         Debug.Log ("left button");
         //save began touch 2d point
         firstPressPos = new Vector2(Input.mousePosition.x,Input.mousePosition.y);

     }
     if (Input.GetMouseButtonUp (0)) {
         //save ended touch 2d point
         secondPressPos = new Vector2 (Input.mousePosition.x, Input.mousePosition.y);

         //create vector from the two points
         currentSwipe = new Vector2 (secondPressPos.x - firstPressPos.x, secondPressPos.y - firstPressPos.y);


         //normalize the 2d vector
         currentSwipe.Normalize ();

         //    desiredPos = Vector3.Lerp (firstPressPos, secondPressPos, Time.deltaTime);
         //swipe left
         if (currentSwipe.x < 0 && currentSwipe.y > -0.5f && currentSwipe.y < 0.5f) {
             Debug.Log ("left swipe");
             if (transform.position.x > -9f) {
                 //    StartCoroutine (move ("left"));
                 /*    spos = transform.position;
                 Debug.Log ("spos" + spos);*/

                 transform.position = new Vector3 (transform.position.x - 9f, transform.position.y, transform.position.z);
                 //transform.Rotate = new Vector3 (0, 0, xAngle);
                 //desiredPos  = Vector3.Lerp (transform.position ,desiredPos  ,Time.deltaTime);
                 //endpos =new Vector3 (transform.position.x - 9f ,transform.position.y,transform.position.z);
                 /*    endpos = new Vector3 (transform.position.x - 9.0f, transform.position.y,transform.position.z);
                 //endpos = transform.position;
                 Debug.Log ("endpos" + endpos);
                 check = true;
                 for (float i = 0.0f; i < 9f; i++) {
                     //transform.position.x = i;
                     Debug.Log ("i");

                     transform.position= new Vector3 (transform.position.x+i, transform.position.y, transform.position.z);
                     check = true; */

             }

         }

         //swipe right
         if (currentSwipe.x > 0 && currentSwipe.y > -0.5f && currentSwipe.y < 0.5f) {

             Debug.Log ("right swipe");
             if (transform.position.x < 9f) {
                 Debug.Log ("spos");
                 //    spos = transform.position;
                 //    Debug.Log ("spos" + spos);
                 //    desiredPos= new Vector3 (transform.position.x +9f,transform.position.y,transform.position.z);
                 //desiredPos     = Vector3.Lerp (transform.position ,desiredPos ,Time.deltaTime);
                 //endpos  = new Vector3 (transform.position.x + 9f,transform.position.y,transform.position.z);
                 transform.position = new Vector3 (transform.position.x + 9f, transform.position.y, transform.position.z);
                 //endpos = transform.position;
                 //check = true;

             }
         }
     }
 }

      
     

}