How do I apply and save my game settings?

I am creating a game settings scene that includes things for volume, resolution and quality. Once I leave the scene all of the changes simply revert, I can't figure out how to keep them saved. I have attempted PlayerPrefs but I could not get it to work .

public class SettingsMenu : MonoBehaviour {

 public AudioMixer audioMixer;

 public Dropdown resolutionDropdown;
 public Dropdown vSyncDropdown;
 public int vSync;

 Resolution[] resolutions;

 void Start()
 {


     resolutions = Screen.resolutions;
     resolutionDropdown.ClearOptions();
     List<string> options = new List<string>();

     int currentResolutionIndex = 0;
     for (int i = 0; i < resolutions.Length; i++)
     {
         string option = resolutions[i].width + " x " + resolutions[i].height;
         options.Add(option);
         if (resolutions[i].width == Screen.currentResolution.width && resolutions[i].height == Screen.currentResolution.height);
         {
             currentResolutionIndex = i;
         }

     }
     resolutionDropdown.AddOptions(options);
     resolutionDropdown.value = currentResolutionIndex;
     resolutionDropdown.RefreshShownValue();
 }

 public void SetResolution(int resolutionIndex)
 {
     Resolution resolution = resolutions[resolutionIndex];
     Screen.SetResolution(resolution.width, resolution.height, Screen.fullScreen);
 }

 public void SetVolume(float volume)
 {
     audioMixer.SetFloat("volume", volume);
 }

 public void SetQuality(int qualityIndex)
 {
     QualitySettings.SetQualityLevel(qualityIndex);
 }

 public void SetFullscreen(bool isFullscreen)
 {
     Screen.fullScreen = !isFullscreen;
 }

 public void SetvSync()
 {
     QualitySettings.vSyncCount= vSync = vSyncDropdown.value;
 }

I also heard that using PlayerPrefs is not a good idea as it is rather vulnerable. Any advice would be appreciated.