How do I fix my FPS movement Script?

So, I followed a tutorial for the movement and the looking, then I applied sliding, with this code:

//Sliding if(Input.GetKey(KeyCode.LeftControl)) { transform.localScale = new Vector3 (1, slideHeight, 1); }else { transform.localScale = new Vector3 (1, normalHeight, 1); }

But then, I can't jump, and the layer mask function (for finding out if there is ground beneath the player) doesn't work. I tried deleting the sliding code, but it still didn't work.

Full code:

 private Rigidbody rb;
 
 public LayerMask layerMask;
 public bool grounded = true;
 public bool isJumpBoost = false;
 
 public float moveSpeed = 6;
 public float slideHeight = 0.5f;
 public float normalHeight = 1.5f;
 
 public float normalJump = 10f;
 public float jumpForce = 10;
 public float boostJump = 30f;
 
 public float maxFall = -55;
 
 // Start is called before the first frame update
 void Start()
 {
     rb = GetComponent<Rigidbody>();
 }

 
 // Update is called once per frame
 void Update()
 {
     float x = Input.GetAxisRaw("Horizontal") * moveSpeed;
     float y = Input.GetAxisRaw("Vertical") * moveSpeed;
     
     grounded = Physics.CheckSphere(new Vector3(transform.position.x, transform.position.y - 1, transform.position.z), 0.4f, layerMask);
     
     if(Input.GetKeyDown(KeyCode.Space) && grounded)
         rb.velocity = new Vector3(rb.velocity.x, jumpForce, rb.velocity.z);
     
     Vector3 movePos = transform.right * x + transform.forward * y;
     Vector3 newMovePos = new Vector3(movePos.x, rb.velocity.y, movePos.z);
     
     rb.velocity = newMovePos;
     
     
     
     if(gameObject.transform.position.y <= maxFall)
     {
         Debug.Log("Player is falling");
         Time.timeScale = 0f;
         //Lose();    
     }
     
     
     //Sliding
     if(Input.GetKey(KeyCode.LeftControl))
     {
         transform.localScale = new Vector3 (1, slideHeight, 1);
     }else
     {
         transform.localScale = new Vector3 (1, normalHeight, 1);
     }
 
 
 }
 
 //Collision Detection
         void OnCollisionEnter(Collision col)
     {
         
         if(col.collider.name == "jumpBoost")
         {    
         jumpForce = boostJump;
         Debug.Log("Player gets a jump boost");
         isJumpBoost = true;
         
         }else
         {
             jumpForce = normalJump;
             Debug.Log("No jump boost now");
             isJumpBoost = false;    
         }
         
     }
 
     //void Lose() this is a function
     //{
             
     //}
 
 

}