player glitching through floor when turning

so i found that my player goes forward okay but when i try and turn he starts to glitch and then eventually falls through the terrain i have tried re-importing the camera and disabling the components on the player one by one but it didn't seem to help here is a video of whats happening https://streamable.com/jfn63

here is all my code please tell me if you require more info

player.cs

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 using UnityEngine.UI;
 
 public class Player : MonoBehaviour {
 
     public Slider HealthBar;
 
     public float CurrentHealth { get; set; }
     public float MaxHealth { get; set; }
 
     public float Speed = 6.0f;
     public float jumpSpeed = 8.0f;
     public float rotateSpeed = 5.0f;
 
     float gravity = 9.8f;
     Vector3 moveDirection = Vector3.zero;
 
     Animator anim;
     CharacterController cc;
 
     static int idleState = Animator.StringToHash("Base Layer.Idle");
     static int moveState = Animator.StringToHash("Base Layer.Walk");
 
     AnimatorStateInfo currentBaseState;
 
     
 
     // Use this for initialization
     void Start () {
 
         MaxHealth = 20f;
         //resets players health on load
         CurrentHealth = MaxHealth;
 
         HealthBar.value = CalculateHealth();
 
         anim = GetComponent<Animator>();
 
         cc = GetComponent<CharacterController>();
 
         if (!anim)
         {
             Debug.Log("No Animator Found.");
         }
 
         if (!cc)
         {
             Debug.Log("No CharacterController Found.");
         }
     }
     
     // Update is called once per frame
     void Update () {
 
 
         anim.speed = Speed;
         //Debug.Log(tag);
         //Debug.Log(Speed);
 
         if (cc.isGrounded)
         {
             float moveForward = Input.GetAxis("Vertical");
 
             moveDirection = new Vector3(0, 0, moveForward);
 
             transform.Rotate(0, Input.GetAxis("Horizontal"), 0);
 
             moveDirection = transform.TransformDirection(moveDirection);
             moveDirection *= Speed;
 
             if (Input.GetButton("Jump")) 
             {
                 moveDirection.y = jumpSpeed;
 
                 anim.SetTrigger("Jump");
             }
             anim.SetFloat("Speed", moveForward);
         }
 
         moveDirection.y -= gravity * Time.deltaTime;
 
         cc.Move(moveDirection * Time.deltaTime);
 
         currentBaseState = anim.GetCurrentAnimatorStateInfo(0);
 
         //if (currentBaseState.fullPathHash == moveState)
         //{
         //    if (Input.GetButtonDown("Fire1"))
         //    {
         //        anim.SetTrigger("Punch");
         //    }
         //}
 
         //if (currentBaseState.fullPathHash == idleState)
         //{
         //    if (Input.GetButtonDown("Fire1"))
         //    {
         //        anim.SetTrigger("Punch");
 
         //        // Instantiate Something
 
         //    }
         //}
 
        
 
         if (Input.GetButtonDown("Jump"))
         {
             anim.SetTrigger("Jump");
         }
 
         while(Input.GetKeyDown(KeyCode.LeftShift))
         {
             Speed = 10;
         }
 
         if (Input.GetKeyDown(KeyCode.E))
         {
             anim.SetTrigger("Dead");
         }
 
         
     }
 
     void OnCollisionEnter(Collision collision)
     {
         
 
         Debug.Log(name);
 
         if (collision.gameObject.name == "Finish")
         {
             Debug.Log("you finished the game");
 
             SceneManager.LoadScene(1, LoadSceneMode.Additive);
         }
 
         if(collision.gameObject.name == "Lava")
         {
             Speed = 5;
             DealDamage(2);
         }
 
         while (collision.gameObject.tag == "Ice")
         {
             Speed = 20;
         }
 
         while (collision.gameObject.tag == "Water")
         {
             Speed = 2;
         }
     }
 
     void DealDamage(float DamageValue)
     {
         CurrentHealth -= DamageValue;
         HealthBar.value = CalculateHealth();
 
         if(CurrentHealth == 0)
         {
             Die();
         }
     }
 
     float CalculateHealth()
     {
         return CurrentHealth / MaxHealth;
     }
 
     void Die()
     {
         CurrentHealth = 0;
         anim.SetTrigger("Dead");
 
     }
 }
 

GameManager.cs

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 public class GameManager : MonoBehaviour {
 
     static GameManager _instance;
 
     // Use this for initialization
     void Start () {
 
         if (instance)
             DestroyImmediate(gameObject);
         else
         {
             DontDestroyOnLoad(gameObject);
             instance = this;
         }
 
         //SceneManager.LoadScene(0, LoadSceneMode.Additive);
 
     }
 
     public static GameManager instance
     {
         get { return _instance; }
         set { _instance = value; }
     }
 
     
     
 
     // Update is called once per frame
     void Update () {
        
 
         
     }
 
     public void StartGame()
     {
         SceneManager.LoadScene("main");
     }
 
     public void Quit()
     {
         Application.Quit();
         Debug.Log("This is where i Would Quit");
     }
 
     public void LoadNewScene(string Scene)
     {
         SceneManager.LoadScene(Scene);
     }
 
     public void MainMenu()
     {
         SceneManager.LoadScene(0);
     }
 }