How to create a difficulty slider/setting for a unity game in a setting scene

I am having a hell of a tie creating a difficulty setting. I have tried a slider and a dropdown and neither have worked. I need a system where a user can decide the difficulty in one scene and then load a level and have the difficulty persist. I have tried statics, playerprefs, and instance. Nothing has worked for me and I'm honestly quite frustrated that there is no tutorial on making a difficulty. Now I'm going to attach my code so that maybe you fellas can help me troubleshoot whats going on. Any Help Is greatly appreciated, thanks! O and I have left in pretty much every attempt I have made at this difficulty thing. So it's a touch messy. using UnityEngine; using UnityEngine.UI; using System.Collections;

public class UIManager : MonoBehaviour { public float difficulty; private Slider diffSlider; private Dropdown diffDropDown; private static UIManager _instance; public static UIManager Instance { get { if(_instance==null){ GameObject go = new GameObject("UIManager"); go.AddComponent(); } return _instance; } } void Awake() { diffSlider = gameObject.GetComponent(); _instance = this; }

 public string level;
 public GameObject HowToPlayText;
 private bool showText;
 public GUIText howToPlayText;
 public float diffSlideAmount;
 string difficultyKey = "Difficulty";

 void Start()
 {
     showText = false;
     HowToPlayText = GameObject.Find("HowToPlayText");
     howToPlayText = GetComponent<GUIText>();
     ShowText();
     diffDropDown.onValueChanged.AddListener(delegate {
         diffDropDownValueChangedHandler(diffDropDown);
     });
 }

 /*public void OnValueChanged(float newValue)
 {
     newValue = diffSlider.value;
     diffSlideAmount = diffSlider.value;
     PlayerPrefs.SetFloat(difficultyKey, diffSlideAmount);
     PlayerPrefs.Save();
     Debug.Log("Difficulty: " + diffSlideAmount);
 }*/




 // Update is called once per frame
 void Update()
 {

 }
 public void OnChoiceChange( )
 {
     if (diffDropDown.value == 0)
     {
         difficulty = 0.25f;
     }
     if (diffDropDown.value == 1)
     {
         difficulty = .5f;
     }
     if (diffDropDown.value == 2)
     {
         difficulty = 1f;
     }
     if (diffDropDown.value == 3)
     {
         difficulty = 3f;
     }
     Debug.Log("Difficulty:" + difficulty);
 }


 public void ShowText()
 {
     if(Input.GetButtonDown("How To Play") && showText == false)
     {
         howToPlayText.enabled = true;

         showText = true;
     }

     if (Input.GetButtonDown("How To Play") && showText == true)
     {
         howToPlayText.enabled = false;
         showText = false;
     }

 }

 void Destroy()
 {
     diffDropDown.onValueChanged.RemoveAllListeners();
 }
 public void LoadLevel(string level)
 {
     Application.LoadLevel(level);
 }
 private void diffDropDownValueChangedHandler(Dropdown target)
 {
     Debug.Log("selected: " + target.value);
 }

 public void SetDropdownIndex(int index)
 {
     diffDropDown.value = index;
 }
 }