Hi Lucas, We use "on top of that" to indicate in addition to something you mentioned earlier. Example: We will be preparing two dishes. On top of that, we will offer you a dessert too. Hope this helps. Cheers, Lance

You have had a bad day and you tell your friend that you were late getting up, your bus was late, you arrived at work late, you missed an important meeting and "on top of that I lost my wallet and money" when I was robbed.