Learn French: Est-ce qu'il part du bureau maintenant ? - Is he leaving from the office now?

In French, when the preposition de (from/of) is followed by the masculine definite article le (the), they must combine into the single word du. You can never write de le in French.

Could I just say part le bureau without the du?

No, because the verb partir (to leave) requires the preposition de when stating the place you are leaving. It acts like 'leaving from' in English. Because de meets le bureau, it forms du bureau.

How can I remember that bureau is masculine, so I know to use du instead of de la?

A very helpful trick for beginners is that almost all French nouns ending in -eau are masculine! Because it is masculine, it takes le, which then forces the contraction with de to become du.

Why is there an apostrophe in qu'il?

The common question starter is Est-ce que. However, when que is followed by a word starting with a vowel, like il (he), the e is dropped and replaced with an apostrophe to make pronunciation smoother. This gives us Est-ce qu'il.