Sau khi chuẩn bị xong, Lan muốn nghỉ một chút trước bữa tiệc.

Sau khi means after. It introduces a time clause.

• Sau = after
• khi = when

So Sau khi chuẩn bị xong means After finishing the preparations or more literally After preparing and finishing.

Vietnamese often puts this time clause at the beginning of the sentence, just like English can:

• After finishing the preparations, Lan wanted to rest a little before the party.

You could also sometimes place the time idea later in the sentence, but the beginning is very natural here.

In Vietnamese, the subject is often omitted when it is obvious from context.

In this sentence, Lan is the person doing the preparation, so Vietnamese does not need to repeat her name:

• Sau khi chuẩn bị xong, Lan muốn...

This is understood as:

• After Lan finished preparing, Lan wanted...

But repeating Lan in the first clause would sound less natural unless you especially wanted to emphasize it.

Chuẩn bị means to prepare.
Xong means finished / completed.

Together, chuẩn bị xong means to finish preparing or to have completed the preparations.

A helpful pattern is:

• verb + xong = finish doing something

Examples:

• ăn xong = finish eating
• làm xong = finish doing
• viết xong = finish writing

So chuẩn bị xong is not just prepare, but specifically finish preparing.

Yes. Sau khi đã chuẩn bị xong is also correct.

Adding đã can emphasize that the action was completed before the next one happened:

• Sau khi đã chuẩn bị xong, Lan muốn nghỉ một chút...

Without đã, the sentence is still perfectly natural and common. Vietnamese often leaves out words like đã when the sequence is already clear from context.

Muốn means to want.

So:

• Lan muốn nghỉ một chút = Lan wants/wanted to rest a little

Vietnamese verbs do not change form for tense, so muốn itself can mean wants or wanted, depending on context. Since the whole sentence describes a situation in sequence, English might translate it as either present or past depending on the larger context.

Both can relate to resting, but there is a small nuance:

• nghỉ = rest, take a break, stop for a while
• nghỉ ngơi = rest in a fuller or more explicit sense

In this sentence, nghỉ một chút sounds very natural because it means take a short break.

If you said:

• Lan muốn nghỉ ngơi một chút that would also be correct, but slightly fuller in tone.

Một chút means a little, for a bit, or a short while.

So:

• nghỉ một chút = rest a little / take a short break

It can describe either:

1. a small amount, or
2. a short duration

Here it mainly refers to a short duration.

Other similar expressions:

• một lát
• một lúc
• một tí

These can all mean something like for a little while, though usage and tone can vary slightly.

Trước bữa tiệc means before the party.

It comes at the end because it tells us when Lan wants to rest:

• Lan muốn nghỉ một chút trước bữa tiệc = Lan wants to rest a little before the party

This is a natural position in Vietnamese. It follows the main action and adds the time reference.

Breakdown:

• trước = before
• bữa tiệc = the party

Tiệc means party or banquet.
Bữa is a classifier-like word often used for meals or occasions of eating/gathering.

So:

• bữa tiệc = the party, especially an event/feast/gathering

You will often see bữa in expressions connected to meals or occasions:

• bữa ăn = meal
• bữa tối = dinner
• bữa tiệc = party/feast

In many contexts, you should learn bữa tiệc as a set phrase.

The comma separates the introductory time clause from the main clause:

• Sau khi chuẩn bị xong, = introductory clause
• Lan muốn nghỉ một chút trước bữa tiệc. = main clause

This is similar to English:

• After finishing the preparations, Lan wanted to rest a little before the party.

In Vietnamese writing, this comma is very common and helps readability.

By itself, the sentence does not clearly mark tense. Vietnamese often relies on context rather than verb changes.

So it could mean:

• After finishing the preparations, Lan wants to rest a little before the party. or
• After finishing the preparations, Lan wanted to rest a little before the party.

In real use, the surrounding sentences usually make the time clear. Vietnamese can add markers like:

• đã for past/completed
• đang for ongoing
• sẽ for future

But they are not always necessary.

Yes, depending on context.

• chuẩn bị can mean to prepare something
• it can also mean to get ready

In this sentence, because of trước bữa tiệc, it probably means Lan was preparing things for the party. But it could also be understood more generally as getting everything ready.

So chuẩn bị xong could be translated as:

• after finishing the preparations
• after getting ready
• after getting everything ready

The best translation depends on the wider context.

Yes, that is grammatical, but the meaning is slightly less specific.

• Sau khi chuẩn bị xong = after finishing the preparation
• Sau khi chuẩn bị = after preparing / after getting ready

Adding xong makes the sense of completion more explicit. It tells the listener clearly that the preparation was completed before Lan wanted to rest.

So in this sentence, xong is very natural because it matches the sequence of events clearly.