PlayerMovement.cs

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

public class PlayerMovement : MonoBehaviour
{
    
    public float speed;         
    private Rigidbody rb;  
    
    void Start()
    {
      rb = GetComponent<Rigidbody>();
    }

    void FixedUpdate()
    {
        float moveHorizontal = Input.GetAxis("Horizontal");
        float moveVertical = Input.GetAxis("Vertical");
        Vector3 movement = new Vector3(moveHorizontal, 0, moveVertical);
        rb.AddForce(movement * speed);
    }
}