Third Person Camera Help?

Hello, I'm making a 3rd person camera and I need it to be limited to the x and Y axis. A example would be the GTA camera, or the Cube World Camera. here's my script, but it does weird things like turn upsidedown and such.

 using UnityEngine;
 using System.Collections;
 
 public class ThirdPersonCamera : MonoBehaviour {
     
     public Transform Player; //What to rotate around
     public float xSpeed = 125.0f; //X sensitivity
     
     public float Limit = 45.0f;
     
     void Update(){
         
         transform.RotateAround(Player.position, Vector3.up, Input.GetAxis("Mouse X") * (xSpeed * Time.deltaTime) );
         transform.RotateAround(Player.position, Vector3.forward, Input.GetAxis("Mouse Y") * (xSpeed * Time.deltaTime) );
         
     }
     
 }