How to move camera in x-z axis only for RTS touch script for mobile ?

Hello,

I am working on RTS based game for mobile. I want to control camera just like "Clash of Clan", I found a tutorial and script by Savalish on youtube. But that was for 2D game. I want that result in 3D so i modified it. Everything is working fine except the camera is moving upward direction that is y-axis. I don't want that. and also need boundaries for limiting camera to move further. Below is the code I used:

 using UnityEngine;
 using System.Collections;
 
 public class TouchCameraControl : MonoBehaviour 
 {
     public float moveSensitivityX = 1.0f;
     public float moveSensitivityY = 1.0f;
     public bool updateZoomSensitivity = true;
     public float orthoZoomSpeed = 0.05f;
     public float minZoom = 1.0f;
     public float maxZoom = 20.0f;
     public bool invertMoveX = false;
     public bool invertMoveY = false;
     public float mapWidth = 60.0f;
     public float mapHeight = 40.0f;
     
     public float inertiaDuration = 1.0f;
     
     private Camera _camera;
 
     private float minX, maxX, minY, maxY;
     private float horizontalExtent, verticalExtent;
     
     private float scrollVelocity = 0.0f;
     private float timeTouchPhaseEnded;
     private Vector3 scrollDirection = Vector3.zero;
 
     void Start () 
     {
         _camera = Camera.main;
 
         maxZoom = 0.5f * (mapWidth / _camera.aspect);
 
         if (mapWidth > mapHeight)
             maxZoom = 0.5f * mapHeight;
 
         if (_camera.fieldOfView > maxZoom)
             _camera.fieldOfView = maxZoom;
 
         CalculateLevelBounds ();
     }
     
     void Update () 
     {
         if (updateZoomSensitivity)
         {
             moveSensitivityX = _camera.fieldOfView / 5.0f;
             moveSensitivityY = _camera.fieldOfView / 5.0f;
         }
 
         Touch[] touches = Input.touches;
 
         if (touches.Length < 1)
         {
             //if the camera is currently scrolling
             if (scrollVelocity != 0.0f)
             {
                 //slow down over time
                 float t = (Time.time - timeTouchPhaseEnded) / inertiaDuration;
                 float frameVelocity = Mathf.Lerp (scrollVelocity, 0.0f, t);
                 _camera.transform.position += -(Vector3)scrollDirection.normalized * (frameVelocity * 0.05f) * Time.deltaTime;
                 
                 if (t >= 1.0f)
                     scrollVelocity = 0.0f;
             }
         }
 
         if (touches.Length > 0)
         {
             //Single touch (move)
             if (touches.Length == 1)
             {
                 if (touches[0].phase == TouchPhase.Began)
                 {
                     scrollVelocity = 0.0f;
                 }
                 else if (touches[0].phase == TouchPhase.Moved)
                 {
                     Vector3 delta = touches[0].deltaPosition;
 
                     float positionX = delta.x * moveSensitivityX * Time.deltaTime;
                     positionX = invertMoveX ? positionX : positionX * -1;
 
                     float positionY = delta.y * moveSensitivityY * Time.deltaTime;
                     positionY = invertMoveY ? positionY : positionY * -1;
 
                     _camera.transform.position += new Vector3 (positionX, 0, positionY);
                     //_camera.transform.position += transform.TransformDirection((Vector2)((new Vector2 (positionX, positionY-positionX))));
                     scrollDirection = touches[0].deltaPosition.normalized;
                     scrollVelocity = touches[0].deltaPosition.magnitude / touches[0].deltaTime;
 
 
                     if (scrollVelocity <= 100)
                         scrollVelocity = 0;
                 }
                 else if (touches[0].phase == TouchPhase.Ended)
                 {
                     timeTouchPhaseEnded = Time.time;
                 }
             }
 
 
             //Double touch (zoom)
             if (touches.Length == 2)
             {
                 Debug.Log ("Double Touch");
                 Vector2 cameraViewsize = new Vector2 (_camera.pixelWidth, _camera.pixelHeight);
 
                 Touch touchOne = touches[0];
                 Touch touchTwo = touches[1];
 
                 Vector2 touchOnePrevPos = touchOne.position - touchOne.deltaPosition;
                 Vector2 touchTwoPrevPos = touchTwo.position - touchTwo.deltaPosition;
 
                 float prevTouchDeltaMag = (touchOnePrevPos - touchTwoPrevPos).magnitude;
                 float touchDeltaMag = (touchOne.position - touchTwo.position).magnitude;
 
                 float deltaMagDiff = prevTouchDeltaMag - touchDeltaMag;
 
                 _camera.transform.position += _camera.transform.TransformDirection ((touchOnePrevPos + touchTwoPrevPos - cameraViewsize) * _camera.fieldOfView / cameraViewsize.y);
 
                 _camera.fieldOfView += deltaMagDiff * orthoZoomSpeed;
                 _camera.fieldOfView = Mathf.Clamp (_camera.fieldOfView, minZoom, maxZoom) - 0.001f;
 
                 _camera.transform.position -= _camera.transform.TransformDirection ((touchOne.position + touchTwo.position - cameraViewsize) * _camera.fieldOfView / cameraViewsize.y);
 
                 CalculateLevelBounds ();
             }
         }
     }
 
     void CalculateLevelBounds ()
     {
         verticalExtent = _camera.fieldOfView;
         horizontalExtent = _camera.fieldOfView * Screen.width / Screen.height;
         minX = horizontalExtent - mapWidth / 2.0f;
         maxX = mapWidth / 2.0f - horizontalExtent;
         minY = verticalExtent - mapHeight / 2.0f;
         maxY = mapHeight / 2.0f - verticalExtent;
     }
 
     void LateUpdate ()
     {
         //Vector3 limitedCameraPosition = _camera.transform.position;
         //limitedCameraPosition.x = Mathf.Clamp (limitedCameraPosition.x, minX, maxX);
         //limitedCameraPosition.y = Mathf.Clamp (limitedCameraPosition.y, minY, maxY);
         //_camera.transform.position = limitedCameraPosition;
     }
 
     void OnDrawGizmos ()
     {
         //Gizmos.DrawWireCube (Vector3.zero, new Vector3 (mapWidth, mapHeight, 0));
     }
 }

Tell me please what is wrong with the code. Any help would appreciated.

Thanks.