Assim que a campainha tocar de novo, a síndica vai abrir o portão.

Assim que means as soon as.

In this sentence, it introduces an action that will happen immediately after another one:

• Assim que a campainha tocar de novo... = As soon as the doorbell rings again...

It is very common in Portuguese for future situations.

Here, tocar is in the future subjunctive.

After expressions like assim que, Portuguese often uses the future subjunctive when talking about something that has not happened yet but is expected to happen in the future.

So:

• Assim que a campainha tocar... = As soon as the doorbell rings...

This may look strange to an English speaker because English does not have a separate future subjunctive form in this kind of sentence.

Compare:

• Quando ele chegar, eu saio. = When he arrives, I’ll leave.
• Se chover, ficamos em casa. = If it rains, we’ll stay home.

In all of these, Portuguese uses the future subjunctive in the subordinate clause.

It looks identical to the infinitive, but in this sentence it is not functioning as an infinitive. It is the future subjunctive form.

For many regular verbs, the future subjunctive is identical in form to the infinitive in some persons, especially:

• eu tocar
• você/ele/ela tocar
• eles/elas tocar em

So in a campainha tocar, the form happens to look like the infinitive, but grammatically it is the future subjunctive.

Vai abrir is the periphrastic future: ir + infinitive.

It means the same basic thing as abrirá:

• A síndica vai abrir o portão.
• A síndica abrirá o portão.

In Brazilian Portuguese, vai abrir is usually more common and more natural in everyday speech.

So:

• vai abrir = very common in conversation
• abrirá = correct, but often more formal or written

De novo means again.

So:

• a campainha tocar de novo = the doorbell ring again

A useful note:

• de novo = again
• novo/nova = new

Examples:

• Tente de novo. = Try again.
• Comprei um carro novo. = I bought a new car.

Síndica is the feminine form of síndico.

In Brazil, a síndico/síndica is the person responsible for managing a condominium or apartment building. Depending on context, English translations might include:

• building manager
• condo manager
• homeowners’ association representative
• superintendent sometimes, though that is not always exact

So a síndica here is probably the woman in charge of the building or condo.

Portão means gate, usually a large entrance gate, often for a building, garage, courtyard, or condo complex.

Porta means door.

So the sentence specifically says the manager will open the gate, not the door.

Examples:

• Abrir a porta = open the door
• Abrir o portão = open the gate

Campainha usually means doorbell or bell.

In this sentence, the most natural interpretation is doorbell.

So:

• a campainha tocar = the doorbell rings

Literally, tocar means to ring here, not to touch. That is another meaning of tocar, but context tells you which one is meant.

The comma separates the introductory clause from the main clause:

• Assim que a campainha tocar de novo, = subordinate clause
• a síndica vai abrir o portão. = main clause

This is very natural when the time clause comes first.

You could also reverse the order:

• A síndica vai abrir o portão assim que a campainha tocar de novo.

In that version, the comma is usually not needed.

Yes, you could, but the meaning shifts slightly.

• Assim que a campainha tocar = as soon as the doorbell rings
• Quando a campainha tocar = when the doorbell rings

Assim que emphasizes immediacy more strongly.

So if you want the idea of right after it rings, assim que is better.

Because a can be different things in Portuguese.

In this sentence:

• a campainha → a = the feminine singular definite article = the
• a síndica → a = again, the

So both campainha and síndica are feminine nouns, which is why they take a.

Compare:

• a campainha
• a síndica
• o portão because portão is masculine

Yes, it sounds natural.

A Brazilian speaker would easily understand it, and the structure is very common:

• Assim que + future subjunctive
• main clause with vai + infinitive

A very natural variation would also be:

• Assim que a campainha tocar de novo, a síndica abre o portão.
• Assim que a campainha tocar novamente, a síndica vai abrir o portão.

All of these work, but the original sentence is perfectly natural.

Yes.

• de novo = again
• novamente = again

So you could say:

• Assim que a campainha tocar novamente, a síndica vai abrir o portão.

The difference is mostly style:

• de novo sounds very common and conversational
• novamente sounds a bit more formal or polished

Both are correct.