why is my player deceleration script not working?

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

public class playermove2 : MonoBehaviour { [SerializeField] private int jumpsleft; [SerializeField] private int jumpsmax; [SerializeField] private bool canjump; [SerializeField] private float jumpheight; [SerializeField] public float movementspeed; [SerializeField] private AnimationCurve acceleration; [SerializeField] private float deceleration; Vector3 vect1; Vector3 vect2; public Rigidbody Playercontroller; private Vector3 velocityplaceholder = Vector3.zero; private float speed;

 public void Awake()
 {
     Playercontroller = gameObject.GetComponent<Rigidbody>();
 }

 private void Update()
 {
     float inputVertical = Input.GetAxisRaw("Vertical");
     float inputHorizontal = Input.GetAxisRaw("Horizontal");
     if (inputHorizontal == 0)

     {
         velocityplaceholder = transform.InverseTransformDirection(Playercontroller.velocity);
         vect1.x = velocityplaceholder.x;
         vect2.y = velocityplaceholder.y;
         Playercontroller.AddForce(Playercontroller.transform.TransformVector(deceleration * vect1));
     }


     if (inputHorizontal == 0 && inputVertical == 0)
     {   
         return;
     }

   

     Vector3 verticalForceToAdd = Playercontroller.transform.forward * inputVertical * movementspeed * Time.deltaTime;
     Vector3 horizontalForceToAdd = Playercontroller.transform.right * inputHorizontal * movementspeed * Time.deltaTime;

     Playercontroller.AddForce(verticalForceToAdd + horizontalForceToAdd);

     
 }

}