Roll a ball camera with rotating by a mouse?

With the Unity tutorial I created a camera that follows a player (ball), but it's only follows in one rotation. I wanna create a camera that not only follows a player, but rotates around a player with mouse. Here's my code: public GameObject player; private Vector3 offset; public int speed;

     private void Start()
     {
         offset = transform.position;
         Cursor.visible = false; //Hides cursor.
     }
 
     private void Update()
     {
         transform.LookAt(player.transform);
         transform.RotateAround(player.transform.position, Vector3.up, Input.GetAxis("Mouse X") * speed);
     }

Thanks in advance!