Check out example codes for "playerprefs not working on android". It will help you in understanding the concepts better.
Code Example 1
// Make sure that it has a default value, like 0 for example
public float Highscore;
public void Start()
{
Highscore = PlayerPrefs.GetFloat("HighScore", 0); // like this
}
public void Start()
{
Highscore = PlayerPrefs.GetFloat("HighScore"); // not like this
}
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