Move camera with touch or mouse click

I am an absolute noob in unity so it might be an easy one. I want to move a camera over a terrain, i did that with this: public class CameraEngine : MonoBehaviour {

     Vector3 hit_position = Vector3.zero;
     Vector3 current_position = Vector3.zero;
     Vector3 camera_position = Vector3.zero;
     float z = 0.0f;
 
     void Start () {
 
     }
 
     void Update(){
         if(Input.GetMouseButtonDown(0)){
             hit_position = Input.mousePosition;
             camera_position = transform.position;
 
         }
         if(Input.GetMouseButton(0)){
             current_position = Input.mousePosition;
             LeftMouseDrag();        
         }
     }
 
     void LeftMouseDrag(){
         current_position.z = hit_position.z = camera_position.y;
 
         Vector3 direction = Camera.main.ScreenToWorldPoint(current_position) - Camera.main.ScreenToWorldPoint(hit_position);
         direction = direction*-1;
 
         Vector3 position = camera_position + direction;
 
         transform.position = position;
     }
 
 }

It works just fine as long as the terrain is watched from a 90 degrees angle from above but i want my camera to have something like 60-70 degrees angle. This beats me, i have no clue how to do that if you can help me i would be very greatefull.