Scriptum/Assets/NPCType.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class NPCType : MonoBehaviour
{

    public GameObject lumberjack;
    public int isQuest;
    public string name;

    void Start()
    {
        NPCDialogue npcdialogue = lumberjack.GetComponent<NPCDialogue>();
        name = npcdialogue.name;

        if (OnMapAppearanceMethod.IsNewGame())
        {
            isQuest = 1;  // TODO I guess we decide here if quest is available for player from the very beginning
        }
        else
        {
            isQuest = PlayerPrefs.GetInt(name + "-S");
        }

        npcdialogue.isQuest = isQuest;
    }

    void Update()
    {
        NPCDialogue npcdialogue = lumberjack.GetComponent<NPCDialogue>();
        isQuest = npcdialogue.isQuest;
        PlayerPrefs.SetInt(name, isQuest);
    }

    public void SaveCheckpoint()
    {
        NPCDialogue npcdialogue = lumberjack.GetComponent<NPCDialogue>();
        isQuest = npcdialogue.isQuest;
        PlayerPrefs.SetInt(name + "-S", isQuest);
    }
}