This seems to be alot simple.. but I'm a beginner and I don't know how to add Main Menu Buttons.

This is in the main class(no errors):

 

package com.tominocz.PAYDAY2;

import java.util.Calendar;
import java.util.Date;

import net.minecraft.client.Minecraft;
import net.minecraft.client.gui.GuiScreen;
import net.minecraft.client.gui.GuiYesNoCallback;
import net.minecraft.client.renderer.texture.DynamicTexture;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.Mod.EventHandler;
import net.minecraftforge.fml.common.event.FMLInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPostInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;

@Mod(modid = PAYDAY2Main.MODID, version = PAYDAY2Main.VERSION)
public class PAYDAY2Main extends GuiScreen implements GuiYesNoCallback
{
    public static final String MODID = "PAYDAY 2 Mod";
    public static final String VERSION = "RELOADED";
private Minecraft mc;
    
    @EventHandler
    public void preinit(FMLPreInitializationEvent event)
    {

    }
    
    @EventHandler
    public void Init(FMLInitializationEvent event)
        {

            boolean flag = true;
            int i = this.height / 4 + 48;
            buttonList.add(new GuiPAYDAY2MenuButton(100, this.width / 2 - 10, i + 72 - 178));
        }
    
    @EventHandler
    public void postinit(FMLPostInitializationEvent event)
    {
    	
    }
}

 

And the main menu is still the same.

Any ideas how to add the button there?

I just started so I'm totally lost in it.

Just begun coding and I'm lost in the coding..

You don't. The main menu, much like capes is sacred territory. Everyone and their brother adding buttons is not the way to go.