How to set the High Score to be the Final Score?

Basically, I currently have a score and a high score. The score varies throughout the game, going up and down. The high score corresponds to the highest score achieved during the game. What I want is for the high score to be the final score that shows when the timer stops.

Here is my Score code:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class ScoreManager : MonoBehaviour
 {
 
     public Text scoreText;
     public Text finalScoreText;
     public Text highScoreText;
 
     public float scoreCount;
     public float finalScoreCount;
     public float highScoreCount;
 
     public float minusPointsPerSecond;
 
     public bool scoreIncreasing;
 
     // Use this for initialization
     void Start()
     {
 
 if (PlayerPrefs.HasKey ("HighScore"))
         {
             highScoreCount = PlayerPrefs.GetFloat("HighScore");
         }
     }
 
     // Update is called once per frame
     void Update()
     {
 
         if (scoreIncreasing)
         {
             scoreCount += minusPointsPerSecond * Time.deltaTime;
         }
 
         if (scoreCount > highScoreCount)
         {
             highScoreCount = scoreCount;
             PlayerPrefs.SetFloat("HighScore", highScoreCount);
         }
 
         scoreText.text = "Score: " + Mathf.Round (scoreCount);
         highScoreText.text = "High Score: " + Mathf.Round (highScoreCount);
     }
      
     public void ResetHighScore()
     {
         scoreCount = 0;
         highScoreCount = 0;
         highScoreCount = scoreCount;
         PlayerPrefs.SetFloat("HighScore", highScoreCount);
     }
 
     public void AddScore (int pointsToAdd)
     {
         scoreCount += pointsToAdd;
     }
 }
 

And here is my Timer code:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class Timer : MonoBehaviour
 {
 
 
     public float myTimer = 0;
     public Text timerText;
     public bool timerIsActive = true;
 
 
     void Start()
     {
         timerText = GetComponent<Text>();
     }
 
     void Update()
     {
         if (timerIsActive)
         {
             myTimer += Time.deltaTime;
             timerText.text = myTimer.ToString("f0");
 
             if (myTimer <= 0)
             {
                 myTimer = 0;
 
 
             }
         }
     }
 }

I'd be really grateful for some ideas on this. Many thanks!