Hey i am trying to add a time score system and time high score system need help.

how do i add timer for score and the highest time the timer reached as my high score? this is what i have tried but i am getting errors anyone want to help?

public class Timer : MonoBehaviour { public Text timertext; public Text highscore;

 private float starttime;

 // Use this for initialization
 void Start () {
     starttime = Time.time;
     highscore = PlayerPrefs.GetFloat("HighScore", 0).ToString;    }
 
 // Update is called once per frame
 void Update () {
     float t = Time.time - starttime;

     string minutes = ((int)t / 60).ToString();
     string seconds = (t % 60).ToString("f2");
     timertext.text = minutes + ":" + seconds;
     PlayerPrefs.SetFloat("Highscore", timertext.text);
 }

}