Après le déjeuner, Paul prend un biscuit, mais Marie préfère un fruit.

Because French usually uses the definite article with meals and times of day.

So:

• après le déjeuner = after lunch
• literally, it is closer to after the lunch, even though English would not normally say that

You may sometimes hear shorter expressions in certain contexts, but après le déjeuner is the standard, natural form here.

Here, déjeuner is a noun, meaning lunch.

It can also be a verb:

• déjeuner = to eat lunch / to have lunch

In this sentence, it is clearly a noun because it comes after le:

• le déjeuner = lunch

A useful note: in standard French from France, déjeuner usually means lunch. In some other French-speaking regions, meal words can vary.

Because prend is the form that matches Paul, which is third person singular.

The verb is prendre = to take / to have

Present tense:

• je prends
• tu prends
• il/elle/on prend

So:

• Paul prend = Paul takes / has

prendre is the infinitive, so it would mean to take, not takes.

French often uses prendre for food and drink when talking about taking, having, or choosing something.

So:

• Paul prend un biscuit can mean Paul takes a biscuit or has a biscuit.
• Paul mange un biscuit would mean Paul actually eats the biscuit.

In other words:

• prendre focuses more on taking/choosing/having
• manger focuses specifically on eating

Both can be possible in different contexts, but prend sounds very natural here.

Because un is the indefinite article for a masculine singular noun.

So:

• un biscuit = a biscuit
• un fruit = a fruit / a piece of fruit

French usually needs an article in cases like this, where English sometimes might not.

Also, both nouns here are masculine:

• un biscuit
• un fruit

That is a very common learner question.

In French, un fruit naturally means one fruit or one piece of fruit. It is completely normal.

In English, we often use fruit as an uncountable noun:

• Marie prefers fruit

But French often uses the countable form when talking about one item:

• Marie préfère un fruit

So this is normal French, even if English would sometimes phrase it differently.

It comes from the verb préférer = to prefer.

The form préfère is the third person singular present tense:

• je préfère
• tu préfères
• il/elle préfère

The accent changes because this verb has a spelling change in some present-tense forms. Compare:

• je préfère
• nous préférons

The è helps show the vowel sound in that form.

No. In this sentence, préférer takes a direct object.

So:

• Marie préfère un fruit = Marie prefers a fruit

There is no à before un fruit here.

If you compare one thing with another, French often uses à:

• Marie préfère un fruit à un biscuit = Marie prefers a fruit to a biscuit

But in your sentence, only the preferred thing is stated, so no preposition is needed.

All three main nouns here are masculine:

• le déjeuner
• un biscuit
• un fruit

That is why you see le and un, not la or une.

For learners, it is best to memorize nouns together with their article:

• le déjeuner
• un biscuit
• un fruit

A rough pronunciation guide is:

• Après le déjeuner → ah-PRAY luh day-zhuh-NAY
• Paul prend un biscuit → Pohl prahn uh(n) bees-KWEE
• mais Marie préfère un fruit → may mah-REE pray-FEHR uh(n) frwee

A few helpful points:

• prend has a nasal vowel; the final d is usually silent
• biscuit sounds roughly like bees-kwee
• fruit sounds like frwee
• French rhythm is smoother than English, so the sentence flows together more than these rough spellings suggest

It does not have to come first.

This sentence is natural:

• Après le déjeuner, Paul prend un biscuit, mais Marie préfère un fruit.

But you could also say:

• Paul prend un biscuit après le déjeuner, mais Marie préfère un fruit.

Putting Après le déjeuner at the beginning gives the time setting first, which is very common and natural in French. The comma after it is also normal in writing.