Learn Portuguese (Portugal): Antes do almoço eu trabalho.

In Portuguese, to say "before [something]", you use the phrase antes de (literally "before of"). Because almoço is a masculine noun, it usually requires the word for "the" (o). The preposition de and the article o combine into do. So, antes do almoço literally translates to "before of the lunch".

Why is there a "the" (o) before lunch? English just says "before lunch".

Portuguese uses definite articles (o or a) much more often than English does, including before meals, days of the week, and even people's names. You will almost always say o almoço instead of just almoço when talking about the meal.

Is trabalho a verb or a noun in this sentence?

It is a verb here! Because it follows the pronoun eu (I), we know it is the "I" form of the verb trabalhar (to work). The noun for "work" or "job" is actually the exact same word: o trabalho.

How does this sentence's word order relate to the question word Quando (When)?

If someone asks you Quando trabalhas? (When do you work?), answering with Antes do almoço eu trabalho is very natural. Putting the time phrase at the very beginning of the sentence puts the focus exactly on the "when" information they asked for. You could also say Eu trabalho antes do almoço, but putting the time first emphasizes it.