Jerky movement of the object

Hey guys,

I´m new to Unity and to this forum. So please excuse me if I do something wrong in the forum. I try to move an object on the x-axis with my fingeran on the z-axis at a fixed speed. I found instructions for this on the internet, but the object moves very jerkily.

I hope someone know a solution,

Thanks in advance

This is my code:

 void FixedUpdate()
     {
         if (Input.touchCount == 1) {
              touch = Input.GetTouch(0);
 
              if (touch.phase == TouchPhase.Moved) {
                  transform.position = new Vector3(
                      transform.position.x + touch.deltaPosition.x * speedModifier,
                      transform.position.y,
                      transform.position.z
                  );
              }
          }
          transform.position = new Vector3(
              transform.position.x, 
              transform.position.y, 
              transform.position.z + (speed * Time.fixedDeltaTime)
              );
     }