回答例

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class PlayerController : MonoBehaviour
{
public float speed = 3f;  //移動スピード
// Start is called before the first frame update
void Start()
{
}
// Update is called once per frame
void Update()
{
float x = Input.GetAxis("Horizontal");  //左右方向のキー取得
float z = Input.GetAxis("Vertical"); //上下方向のキー取得
float addX = speed * x * Time.deltaTime;
float addZ = speed * z * Time.deltaTime;
transform.GetComponent<Rigidbody>().MovePosition(transform.position + new Vector3(addX, 0, addZ));
transform.LookAt(transform.position + new Vector3(addX, 0, addZ));
}
}