How do I read and write non-static variables from a different class?

I am making a game where i save the player's settings in a json file. But i cant figure out how to access the variables in the classes i save. The variables cant be static because then i cant save them.

The save script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using System.IO;
 
 public static class SaveManager
 {
     public static void save(Total total)
     {
         string dir = Application.persistentDataPath + "/SaveData/";
         
         if(!Directory.Exists(dir))
         {
             Directory.CreateDirectory(dir);
         }
         
         string json = JsonUtility.ToJson(total, true);
         File.WriteAllText(dir + "Saves.json", json);
     }
     
     public static Total load()
     {
         string fullPath = Application.persistentDataPath + "/SaveData/" + "Saves.json";
         Total total = new Total();
         
         if(File.Exists(fullPath))
         {
             string json = File.ReadAllText(fullPath);
             total = JsonUtility.FromJson<Total>(json);
         }else
         {
             Debug.Log(fullPath + "Doesnt exist");
         }
         
         return total;
     }
 }

The script with save and load functions and the classes to save:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class SaveScript : MonoBehaviour
 {
    public Total total;
    
    public void save()
    {
         SaveManager.save(total);
         Debug.Log("saved");
    }
    
    public void load()
    {
         total = SaveManager.load();
         Debug.Log("loaded");
    }
    
 }
 
 [System.Serializable]
 public class Settings
 {
     public int quality = 2;
     public int fullscreenMode = 0;
     public float masterVolume = 1f;
     public float musicVolume = 0.5f;
 }
 
 [System.Serializable]
 public class SystemVars
 {
     public int yes;
 }
 
 [System.Serializable]
 public class Info
 {
     public string yes = "nothing yet";
 }
 
 [System.Serializable]
 public class Total
 {
     public Settings Settings;
     public SystemVars System;
     public Info Info;
 }

And the settings script: using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.Audio; using UnityEngine.UI;

 public class SetSettings : MonoBehaviour
 {
     public AudioMixer audioMixer;
     
     public SaveScript saveScript;
     
     void Start()
     {    
         saveScript = GameObject.Find("Save").GetComponent<SaveScript>();
         saveScript.load();
         setAll();
     }
     
     public void setQuality(int qualityIndex)
     {
         QualitySettings.SetQualityLevel(qualityIndex, true);
     }
     
     public void setFullscreenMode(int fullscreenMode)
     {
         var nothing = fullscreenMode switch
         {
             0 => Screen.fullScreenMode = FullScreenMode.ExclusiveFullScreen,
             1 => Screen.fullScreenMode = FullScreenMode.FullScreenWindow,
             2 => Screen.fullScreenMode = FullScreenMode.MaximizedWindow,
             3 => Screen.fullScreenMode = FullScreenMode.Windowed,
             _ => Screen.fullScreenMode = FullScreenMode.FullScreenWindow
         };
     }
     
     public void setMasterVolume(float masterVolume)
     {
         GameObject.Find("Canvas").GetComponent<SetText>().setMasterVolumeText();
         audioMixer.SetFloat("masterVolume", Mathf.Log10 (masterVolume) * 20);
     }
     
     public void setMusicVolume(float musicVolume)
     {
         GameObject.Find("Canvas").GetComponent<SetText>().setMusicVolumeText();
         audioMixer.SetFloat("musicVolume", Mathf.Log10 (musicVolume) * 20);
     }
     
     public void restoreDefaults()
     {
         setQuality(2);
         setFullscreenMode(0);
         setMasterVolume(1f);
         setMusicVolume(0.5f);
     }
     
     public void setAll()
     {    //Take the values from settings class and assign them in functions
             setQuality(s.quality);
         //    Debug.Log(s.quality);
             setFullscreenMode(s.fullscreenMode);
         //    Debug.Log(s.fullscreenMode);
             setMasterVolume(s.masterVolume);
         //    Debug.Log(s.masterVolume);
             setMusicVolume(s.musicVolume);
         //    Debug.Log(s.musicVolume);
         //    GameObject.Find("Canvas").GetComponent<SetText>().quality.value = s.quality;
         //    GameObject.Find("Canvas").GetComponent<SetText>().fullscreenMode.value = s.fullscreenMode;
         //    GameObject.Find("Canvas").GetComponent<SetText>().masterVolumeSlider.value = s.masterVolume;
         //    GameObject.Find("Canvas").GetComponent<SetText>().musicVolumeSlider.value = s.musicVolume;
     }
 }

Can someone please tell me how i can change and read the files in the Savescript class from the SetSettings class?