Snake Movement Problem

Well i have these code that should've make my snake move, for note i follow a youtube tutorial Here Is The Link. Well i'm facing a problem as he did at the 58.48 Minute, but i didn't see him giving a solution for it, so i tried it my self. But i ended up with no solution as well, please if you guys could help me i appreciate it so much. I've been stuck in this for weeks already :"

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class SnakeMovement : MonoBehaviour
 {
     [Header("Manager : ")]
     [SerializeField] private GameController gameController;
 
     [Space]
 
     [Header("Snake Properties : ")]
     [SerializeField] public List<Transform> m_BodyParts = new List<Transform>();
     [SerializeField] private float m_MinDistance = 0.25f;
     [SerializeField] private float m_DistanceBetweenBodyParts;
     [SerializeField] private int m_InitialBody;
     [SerializeField] public float m_Speed = 7.0f;
     [SerializeField] private float m_RotationSpeed = 50.0f;
     [SerializeField] private float m_LerpTimeX;
     [SerializeField] private float m_LerpTimeY;
 
     [Space]
 
     [Header("Snake Head Prefab : ")]
     public GameObject m_BodyPrefab;
 
     [Space]
 
     [Header("Parts TextAmount Management : ")]
     public TextMesh m_PartsAmountTextMesh;
 
     [Space]
 
     [Header("Mouse Control :")]
 
     Vector2 m_MousePreviousPosition;
     Vector2 m_MouseCurrentPostion;
 
     [Space]
 
     [Header("Particle System : ")]
 
     public ParticleSystem m_SnakeParticle;
 
     /// <summary>
     /// PrivateField
     /// </summary>
 
     private Transform m_CurrentBodyPart;
     private Transform m_PreviousBodyPart;
     private bool m_bFirstPart = true;
     private Vector3 m_LastPosition;
     private float m_TimeRemaining = 10.0f;
 
     private void Awake()
     {
         m_bFirstPart = true;
 
         if (m_bFirstPart)
             Invoke("SpawnBodyPart", 0.1f);
 
     }
 
     private void Start()
     {
 
         m_LastPosition = m_BodyParts[0].transform.position;
 
     }
 
     private void Update()
     {
 
         if (GameController.m_GameState == GameController.GameState.GAME)
         {
 
             if (m_PartsAmountTextMesh != null)
                 m_PartsAmountTextMesh.text = m_BodyParts.Count + "";
 
             if (m_BodyParts.Count >= 1)
                 m_PartsAmountTextMesh.transform.position = new Vector3(m_BodyParts[0].position.x, m_BodyParts[0].position.y + 0.5f, 0);
 
             if (m_BodyParts.Count == 0 && m_bFirstPart == false)
                 gameController.SetGameOver();
         }
 
         float Distance = Vector3.Distance(m_LastPosition, m_BodyParts[0].position);
 
         if (m_TimeRemaining > Time.deltaTime)
         {
 
             m_TimeRemaining -= Time.deltaTime;
 
         }
         else
         {
             
 
             Debug.Log(Distance);
             m_TimeRemaining = 10.0f;
 
             m_LastPosition = m_BodyParts[0].position;
         }
     }
 
     private void FixedUpdate()
     {
 
         if (GameController.m_GameState == GameController.GameState.GAME) Movement();
 
     }
 
     public void SpawnBodyPart()
     {
 
             for (int i = 0; i < m_InitialBody; i++)
                 Invoke("AddBodyPart", 0.1f);
 
     }
 
     public void Movement()
     {
 
         float l_CurSpeed = m_Speed;
         float l_MaxX = Camera.main.orthographicSize * Screen.width / Screen.height;
 
         if (m_BodyParts.Count > 0)
             m_BodyParts[0].Translate(Vector2.up * l_CurSpeed * Time.smoothDeltaTime);
 
         if (m_BodyParts.Count > 0)
         {
 
             if (m_BodyParts[0].position.x > l_MaxX)
                 m_BodyParts[0].position = new Vector3(l_MaxX - 0.1f, m_BodyParts[0].position.y, m_BodyParts[0].position.z);
 
             else if (m_BodyParts[0].position.x < -l_MaxX)  
                 m_BodyParts[0].position = new Vector3(-l_MaxX + 0.1f, m_BodyParts[0].position.y, m_BodyParts[0].position.z);
         
         }
 
         if (Input.GetMouseButtonDown(0))
             m_MousePreviousPosition = Camera.main.ScreenToWorldPoint(Input.mousePosition);
         else if (Input.GetMouseButton(0))
         {
 
             if (m_BodyParts.Count > 0 && Mathf.Abs(m_BodyParts[0].position.x) < l_MaxX)
             {
                 m_MouseCurrentPostion = Camera.main.ScreenToWorldPoint(Input.mousePosition);
 
                 float l_DeltaMousePosition =  Mathf.Abs(m_MousePreviousPosition.x - m_MouseCurrentPostion.x );
                 float l_Sign = Mathf.Sign(m_MousePreviousPosition.x - m_MouseCurrentPostion.x);
 
                 Vector2 Position = (Vector2.right * m_RotationSpeed * l_DeltaMousePosition * -l_Sign);
                 m_BodyParts[0].GetComponent<Rigidbody2D>().AddForce(Position * l_CurSpeed);
                 m_MousePreviousPosition = m_MouseCurrentPostion;
 
             }
             else if (m_BodyParts.Count > 0 && m_BodyParts[0].position.x > l_MaxX)
                 m_BodyParts[0].position = new Vector3(l_MaxX - 1f, m_BodyParts[0].position.y, m_BodyParts[0].position.z);
 
             else if (m_BodyParts.Count > 0 && m_BodyParts[0].position.x < l_MaxX)
                 m_BodyParts[0].position = new Vector3(-l_MaxX + 1f, m_BodyParts[0].position.y, m_BodyParts[0].position.z);
 
         }
 
         /*
          * To Make The Rest Of The Body Following The Head
          */
         for (int i = 1; i < m_BodyParts.Count; i++)
         { 
 
                 m_CurrentBodyPart = m_BodyParts[i];
 
                 if (m_BodyParts.Count > 1)
                     m_PreviousBodyPart = m_BodyParts[i - 1];
 
                 Vector3 l_NewPost = m_PreviousBodyPart.position;
 
                 l_NewPost.z = m_BodyParts[0].position.z;
 
                 Vector3 l_Position = m_CurrentBodyPart.position;
 
                 l_Position.x = Mathf.Lerp(l_Position.x, l_NewPost.x, m_LerpTimeX);
                 l_Position.y = Mathf.Lerp(l_Position.y, l_NewPost.y - m_DistanceBetweenBodyParts, m_LerpTimeY);
 
                 m_CurrentBodyPart.position = l_Position;
                 
         }
 
     }
 
     /// <summary>
     /// Adding Body Part To Snake Body
     /// </summary>
     public void AddBodyPart()
     {
 
         Transform l_NewPart;
 
         if (m_bFirstPart)
         {
 
             l_NewPart = (Instantiate(m_BodyPrefab, new Vector3(0, 0, 0), Quaternion.identity) as GameObject).transform;
 
             m_PartsAmountTextMesh.transform.parent.position = l_NewPart.position + new Vector3(0, 1.5f, 0);
 
             m_bFirstPart = false;
             Debug.Log(m_bFirstPart);
 
         }
         else
         {
 
             l_NewPart = (Instantiate(m_BodyPrefab, m_BodyParts[m_BodyParts.Count - 1].position, m_BodyParts[m_BodyParts.Count - 1].rotation) as GameObject).transform;
 
             l_NewPart.SetParent(transform);
 
         }
 
         m_BodyParts.Add(l_NewPart);
 
 
     }
 }