How to restart game when player lose?

Question

am making a simple in which you drag a player on screen and when a ball hits you you lose ,so you have to move the player away from the balls.level zero:no balls, level one:there is one ball on screen, level two: two balls on screen,the level increases when you reach certain scores. the problem here when player loses the game restart at level 2 and not at level 0.here is my code:

public class MyGdxGame extends ApplicationAdapter implements InputProcessor{

// variables
public int[] x={0,0};
public int[] y={0,300};
public int[] size={100,50};
public Ball ball1,ball2;
public Player player;
// Checker: Checks if Ball Hits Player
public Checker checker;
public Texture background;
public Stage stage;

// creation of application
@Override
public void create () {
    checker=new Checker();
    player =new Player();
    background=new Texture(Gdx.files.internal("background.png"));
    stage = new Stage();
    // Ball(x, y, size , speedX, speedY)
    ball1=new Ball(x[0],y[0],size[0],10,10);
    ball2=new Ball(x[1],y[1],size[1],20,10);
}

// changement of application
@Override
public void render () {
    Gdx.gl.glClearColor(1,1,1,1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

    stage.getBatch().begin();
    stage.getBatch().draw(background,0,0,Gdx.graphics.getWidth(),Gdx.graphics.getHeight());
    stage.addActor(player);
    if(checker.level>0)stage.addActor(ball1);
    if(checker.level>1)stage.addActor(ball2);
    stage.getBatch().end();

    // Checks if Ball Hits Player
    if(checker.check1(player,ball1)){lost();}
    if(checker.check1(player,ball2)){lost();}

    // score increases
    checker.score();

    stage.act(Gdx.graphics.getDeltaTime());
    stage.draw();

    Gdx.input.setInputProcessor(this);
}
// Moethod Called When you lose
public void lost(){
    checker.level=0;
    checker.score=0;
}

// Drag Listener
@Override
public boolean touchDragged(int screenX, int screenY, int pointer) {
    player.updatePosition(screenX,screenY);
    return true;
}

// releasing memory of the app
@Override
public void dispose () {
    stage.dispose();
}

Answer 1

You call stage.addActor(ball1) but never call ball1.remove() inside lost().

Same for ball2.

// Method called when you lose
public void lost(){
    checker.level=0;
    checker.score=0;
    ball1.remove();
    ball2.remove();
}