Hello and sry 4 my silly questions again.

I tried a normal drop as well but it dont works..

I'm familiar with the codes from 1.6... but 1.8 is different. v.v

I tried to update the 1.6 code to 1.8:

public class ItemLooting {
    public static double rand;
    public Random r = new Random();


    public void onEntityDrop(LivingDropsEvent event) {
  	  if(event.entityLiving instanceof EntityCreeper) {
  		  event.entityLiving.dropItem(BasicEWM.fireCore, r.nextInt(2));
  	  }
    }
            
}

And add this to my ModDatabase:

MinecraftForge.EVENT_BUS.register(new ItemLooting());

You need to add the @SubscribeEvent annotation above your event method, and Random#nextInt(2) gives you a value of either 0 or 1, so you might be adding a stack of size 0; probably want to add 1 to the result, or use it as the condition.