Que sorte, o elevador voltou a funcionar.

No verb is missing. Que sorte is a very common exclamation in Portuguese, similar to How lucky!, What luck!, or Good thing! in English.

Portuguese often allows short exclamatory expressions like this without a verb. So Que sorte works as a complete emotional reaction before the speaker adds the rest of the information.

In this sentence, it sets the tone first: the speaker is reacting positively to what happened.

The comma separates the exclamation Que sorte from the main statement o elevador voltou a funcionar.

It works a bit like saying in English:

• What luck, the elevator is working again.

The comma shows a pause between the emotional reaction and the explanation of why the speaker feels that way.

Portuguese uses articles very often, more often than English does. Here o elevador means the elevator, referring to a specific elevator that both speaker and listener can identify.

In English, sometimes we can sound natural without an article in certain situations, but in Portuguese you usually need one here.

So:

• o elevador = the elevator
• um elevador = an elevator

Using o suggests it is a known, specific elevator, probably the one in the building they are in.

This is a very useful structure:

• voltar a + infinitive

It means to do something again or to resume doing something.

So:

• voltar a funcionar = to work again, to start working again, to resume functioning

In this sentence, the idea is that the elevator had stopped working before, and now it is functioning again.

This is more natural in Portuguese than translating word-for-word as returned to function.

Because the verb voltar commonly forms this pattern:

• voltar a + infinitive

The a is part of the verbal construction. It is not optional here.

Examples:

• Voltei a estudar. = I started studying again / I went back to studying.
• Ela voltou a correr. = She started running again.
• O elevador voltou a funcionar. = The elevator started working again.

So after voltou, Portuguese uses a before the infinitive.

Voltou is the preterite form of voltar. The preterite is used because the speaker is talking about a completed event: at some point, the elevator changed from not working to working again.

So the sentence focuses on that completed change.

If you used the imperfect instead, it would suggest an ongoing or habitual background action, which would not fit as well here.

Both can express a similar general idea, but voltar a funcionar is the more natural and common way to say that something resumed working after a period of not working.

Compare:

• voltou a funcionar = started working again / resumed functioning
• funcionou de novo = worked again

The second one is possible in some contexts, but it can sound less natural here because the important idea is the return to a working state, not just one isolated moment of functioning.

So voltou a funcionar is the idiomatic choice.

Yes. That is completely natural.

Using:

• Que sorte! O elevador voltou a funcionar.

makes the exclamation feel more separate and a bit stronger.

Using:

• Que sorte, o elevador voltou a funcionar.

connects the reaction and the explanation more smoothly in one sentence.

Both are good. The difference is mostly punctuation and rhythm.

Yes. For example:

• O elevador voltou a funcionar. Que sorte!
• Que sorte que o elevador voltou a funcionar.

These versions are also natural, but they are slightly different in structure and emphasis.

• Que sorte, o elevador voltou a funcionar.
  starts with the emotional reaction.

• O elevador voltou a funcionar. Que sorte!
  gives the fact first, then the reaction.

• Que sorte que o elevador voltou a funcionar.
  uses que to introduce the clause more explicitly, like How lucky that the elevator started working again.

It is broader than just machines.

Funcionar can mean:

• to function
• to work
• to operate
• to be effective

Examples:

• O elevador não funciona. = The elevator does not work.
• Meu celular voltou a funcionar. = My phone started working again.
• Essa ideia funciona. = That idea works.
• O plano não funcionou. = The plan did not work.

So in this sentence it is about a machine, but the verb is useful in many situations.

In standard Brazilian pronunciation, voltou is roughly:

• vol-TOH

The stress is on the last syllable: tou.

A few pronunciation notes:

• vol sounds like vow or vohl, depending on accent
• tou sounds like toh with stress
• the final u sound is not like English oo here; it is part of the diphthong in tou

A learner-friendly approximation would be:

• vohl-TOH

Yes, very naturally.

If someone tells you good news, you can simply reply:

• Que sorte!

It works as a standalone reaction, just like How lucky! or Nice! depending on context.

So in this sentence, Que sorte could either introduce the statement or stand alone as a complete exclamation.