SWING - skip from file to file and repaint everything?

[Nozz]

Hi.
I have little problem. I want to erase everything from my screen and paint everything what is in another file.
I have something like that:
Menu:

package jumperSwing;
// DRAW MENU CONTENT IN PANEL

import java.awt.*;

import javax.swing.JPanel;
import javax.swing.JButton;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Menu extends JPanel implements ActionListener{

	private static final long serialVersionUID = 1L;
	
	private JButton start;
	private JButton exit;
	 
	private BufferedImage MenuBG;
	
	 public Menu() {
	        super();
	        setLayout(new FlowLayout(FlowLayout.CENTER, 15, 15));
	 
	        File imageFile = new File("images/sky.jpg");
	        try {
	        	MenuBG = ImageIO.read(imageFile);
	        } catch (IOException e) {
	            System.err.println("Image Error");
	            e.printStackTrace();
	        }
	
		 start = new JButton("Start");
		 exit = new JButton("Exit");
		 
	     start.addActionListener(this);
	     exit.addActionListener(this);
	        
		 add(start);
		 add(exit);
	 }
	 

	 
	   @Override
	    public void actionPerformed(ActionEvent e) {
	        Object click = e.getSource();
	        if(click == start){
	        	//skip to game
	        }
	        else if(click == exit)
	            System.exit(0);
	    }
	 
	 @Override
	 protected void paintComponent(Graphics g) {
	     super.paintComponent(g);
	     Graphics2D g2d = (Graphics2D) g;
	     g2d.drawImage(MenuBG, 0, 0, this);
	 }
	 
}

Game:

package jumperSwing;
// DRAW GAME CONTENT IN PANEL

import java.awt.*;

import javax.swing.JPanel;
import javax.swing.JButton;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Game extends JPanel implements ActionListener{

	private static final long serialVersionUID = 1L;

	private JButton jump;
	 
	private BufferedImage GameBG;
	
	 public Game(){
	        super();
	        setLayout(new FlowLayout(FlowLayout.CENTER, 15, 15));

	 
	        File imageFile = new File("images/sky2.jpg");
	        try {
	        	GameBG = ImageIO.read(imageFile);
	        } catch (IOException e) {
	            System.err.println("Image Error");
	            e.printStackTrace();
	        }
	
		 jump = new JButton("Jump");
		 
		 jump.addActionListener(this);
	        
		 add(jump);

	 }
	 

	 
	   @Override
	    public void actionPerformed(ActionEvent e) {
	        Object click = e.getSource();
	        if(click == jump){
		        // jump + points
	        }
	   }
	 
	 @Override
	 protected void paintComponent(Graphics g) {
	     super.paintComponent(g);
	     Graphics2D g2d = (Graphics2D) g;
	     g2d.drawImage(GameBG, 0, 0, this);
	 }
	 
}

There is comment "//skip to game" in Menu, where I want put jump to Game file, but I have no idea how.
I tried to use this:

JPanel game = new Game();
add(game);

But It can't do anything.
Also tried:

validate();
repaint();
JPanel menu = new Menu();
add(menu);

But it just draw "jump" button in first free place(just like new button cause of flowlayout).
So. How can I stop and erase menu and paint game instead?

// Yea yea, I know maybe it doesnt make sense now to create 2 files with same things, but I just want to know how to do this and then I will change almost everything in Game ofc :P