So, I was just trying to add jump function to my game, but somehow it jumps twice everytime, I checked and the 'isGrounded' stays as true even when the player is in air.. Here's the code

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 [RequireComponent(typeof(Rigidbody))]
 public class PlayerController : MonoBehaviour
 
 {
     // Floats and variables
     [SerializeField]
     private float speed = 5f;
     private float xMov;
     private float zMov;
 
 
     public Vector3 Jump;
     [SerializeField]
     public float JumpForce = 2f;
     public bool isGrounded;
     Rigidbody rb;
 
 
     // Start is called atr the start of the game
      void Start()
     {
         rb = GetComponent<Rigidbody>();
         Jump = new Vector3(0f, 2f, 0f);
     }
 
     void OnCollisionStay()
     {
         isGrounded = true;
     }
 
     // Update is called once per frame
     void Update()
     {
         //Movement
         xMov = Input.GetAxis("Horizontal");
         zMov = Input.GetAxis("Vertical");
 
         Vector3 movementValue = new Vector3(xMov, 0.0f, zMov);
         transform.position += (movementValue * speed * Time.deltaTime);
 
         if (Input.GetKeyDown(KeyCode.Space) && isGrounded)
         {
             isGrounded = false;
             rb.AddForce(Jump * JumpForce, ForceMode.Impulse);
             isGrounded = false;
         }
     }
 }