Learn French: Est-ce que tu as déjà faim ?

In English, we use 'to be' for physical states, but French uses avoir (to have). The word faim is actually a noun meaning 'hunger'. So instead of saying 'Are you hungry?', French speakers literally ask 'Do you have hunger?'.

What is the purpose of est-ce que at the start of the sentence?

Est-ce que is a very common phrase used to turn a regular statement into a yes-or-no question. If you drop it, you just have the statement tu as déjà faim (you are already hungry). Putting est-ce que at the very beginning is like a clear signal that a question is coming.

Why is the word déjà placed right in the middle of as faim?

In French, short adverbs like déjà (already) are usually placed immediately after the conjugated verb. Here, it naturally goes right after the verb as and before the noun faim.