How to set text when i want?

So i have a highscore text that i want to change when the player loses (later i wanna add live score track aswell)
But i cant seem to figure out how to do it, this is the but in the code that are meant to change the highscore text

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class groundController : MonoBehaviour {

    
    public GameObject spawner;
    public GameObject greenBall;
    public GameObject redBall;
    public GameObject yellowBall;
    public Text highScoreText;

    void Start ()
    {
        
    }
	
	
	void Update ()
    {
        greenBall = GameObject.FindGameObjectWithTag("greenBall");
        redBall = GameObject.FindGameObjectWithTag("redBall");
        yellowBall = GameObject.FindGameObjectWithTag("yellowBall");
        Debug.Log(yellowBall);
        
    }

    void OnTriggerEnter2D(Collider2D other)
    {
        if (other.gameObject.tag == "greenBall")
        {
            GameOver();
        }
        else if (other.gameObject.tag == "yellowBall")
        {
            Destroy(other.gameObject);
        }
        else if(other.gameObject.tag == "redBall")
        {
            Destroy(other.gameObject);
        }
    }

    public void GameOver()
    {
        spawner.GetComponent<gameController>().playable = false;
        Destroy(greenBall);
        Destroy(redBall);
        Destroy(yellowBall);
        if (spawner.GetComponent<gameController>().Score > spawner.GetComponent<gameController>().highScore)
        {
            spawner.GetComponent<gameController>().highScore = spawner.GetComponent<gameController>().Score;
            highScoreText = "Highscore: " + spawner.GetComponent<gameController>().highScore;
        }
        else if(spawner.GetComponent<gameController>().Score == spawner.GetComponent<gameController>().highScore)
        {

        }
        else if(spawner.GetComponent<gameController>().Score < spawner.GetComponent<gameController>().highScore)
        {
            
        }
       
    }

    void ClearBalls()
    {
        if(spawner.GetComponent<gameController>().playable == false)
        {
            Destroy(greenBall);
            Destroy(redBall);
            Destroy(yellowBall);
        }
    }

}

I KNOW I KNOW it is gore to a someone that know what they are doing but it works for me.

But i am getting the error "Cannot implicitly convert type ‘string’ to ‘Unity.Engine.UI.Text’ " (Line 54)

Any help here ?

it should be

highScoreText.text = "Highscore: " + spawner.GetComponent<gameController>().highScore;

don’t forget that .text after your reference

Dont forget to accept the answer if it worked