i have a problem with brackeys tuturial (E7) with the score

using UnityEngine;
using UnityEngine.UI;

public class score : MonoBehaviour {

public Transform player;
public Text scoreText;

// Update is called once per frame
void Update () {
    scoreText.text = player.position.z.ToString();
}

}

you are using TextMeshPro Text, so your code should be

using TMPro;
using UnityEngine; 
using UnityEngine.UI;

public class score : MonoBehaviour {

 public Transform player;
 public TMP_Text scoreText;
 // Update is called once per frame
 void Update () {
     scoreText.text = player.position.z.ToString();
 }