is it possible to create a variable that contains all worlds and if so how?
   
   
            public void hitGegnerBullet()
    {
        Actor GegnerBullet = getOneIntersectingObject(GegnerBullet.class);
        if(GegnerBullet != null)
        {
            
            World myWorld2= getWorld();
            Level1 level1 = (Level1)myWorld2;
            HealthBar healthbar =level1.getHealthBar();
            if(hitGegnerBullet == false)
            {
                healthbar.loseHealth();
                hitGegnerBullet = true;
                if(healthbar.health <=0)
                {
                    leben = 0;
                }
            } else {
                hitGegnerBullet = false;
            }
        }
    
    }int gegnersSpawned;
int maxGegners = 10; // adjust as needed
public void addGegner()
{
    if (gegnersSpawned < maxGegners)
    {
        addObject(new Gegner(), 100, 100); // wherever
        gegnersSpawned++;
    }
}
public void checkEndWave()
{
    if (gegnersSpawned == maxGegners && getObjects(Gegner.class).isEmpty())
    {
        // end wave
    }
}