FPS Controller rotation,FPS Controller rotation problem

1. Sorry for bad English :) I'm from Slovenia.

2. I create my first 3d game and I followed Bracky tutorial ( https://www.youtube.com/watch?v=_QajrabyTJc ) Something works like looking up and down but if I want to move the mouse to left it goes for 1 sec but than glitched back to the center. Please help :) Thanks here is my code:

   using System.Collections; using System.Collections.Generic; using UnityEngine;

   public class MouseLook : MonoBehaviour {

     public float mouseSensitivity = 100f;
    
        public Transform playerBody;
    
        float xRotation = 0f;
    
        // Start is called before the first frame update
        void Start()
        {
            Cursor.lockState = CursorLockMode.Locked;
        }
    
        // Update is called once per frame
        void Update()
        {
            float mouseX = Input.GetAxis("Mouse X") * mouseSensitivity * Time.deltaTime;
            float mouseY = Input.GetAxis("Mouse Y") * mouseSensitivity * Time.deltaTime;
    
            xRotation -= mouseY;
            xRotation = Mathf.Clamp(xRotation, -90f, 90f);
    
            transform.localRotation = Quaternion.Euler(xRotation, 0f, 0f);
            playerBody.Rotate(Vector3.up * mouseX);
        }
    }
   
   
   
   
   
   

, 1. Sorry for bad English, I'm from Slovenia :). 2. So I want to make 3d game and I follow the Bracky tutorial. ( https://www.youtube.com/watch?v=_QajrabyTJc ) I type everything just like he and it's not working well. My rotation in Y is working (up and down) but in X (left and right) not. If I drag the mouse in left or right it goes for 1 sec and glitched back in center.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class MouseLook : MonoBehaviour
 {
 
     public float mouseSensitivity = 100f;
 
     public Transform playerBody;
 
     float xRotation = 0f;
 
     // Start is called before the first frame update
     void Start()
     {
         Cursor.lockState = CursorLockMode.Locked;
     }
 
     // Update is called once per frame
     void Update()
     {
         float mouseX = Input.GetAxis("Mouse X") * mouseSensitivity * Time.deltaTime;
         float mouseY = Input.GetAxis("Mouse Y") * mouseSensitivity * Time.deltaTime;
 
         xRotation -= mouseY;
         xRotation = Mathf.Clamp(xRotation, -90f, 90f);
 
         transform.localRotation = Quaternion.Euler(xRotation, 0f, 0f);
         playerBody.Rotate(Vector3.up * mouseX);
     }
 }