A convidada vai trazer um presente para a festa.

A is the feminine singular definite article, meaning the.

The noun convidada is feminine singular, so the article must match it:

• a convidada = the female guest
• o convidado = the male guest

Unlike English, Portuguese usually marks gender on articles and often on nouns/adjectives too.

Convidada means guest or invited woman.

It is the feminine form of:

• convidado = male guest
• convidada = female guest

The ending -a often marks feminine nouns/adjectives in Portuguese, though not always. In this sentence, it clearly shows that the guest is female.

Vai trazer is a very common way in Brazilian Portuguese to express the future. It is the structure:

• ir + infinitive

So:

• vai trazer = is going to bring / will bring

Here:

• vai = third-person singular of ir (to go)
• trazer = to bring

Other possible forms:

• traz = brings / is bringing depending on context
• trará = simple future, more formal or written

In everyday Brazilian Portuguese, vai trazer is extremely natural.

Because the subject is singular: a convidada.

The verb ir has to agree with the subject:

• a convidada vai trazer = the guest is going to bring
• as convidadas vão trazer = the guests are going to bring

So vai matches one person.

This is a very common question.

• trazer = to bring → movement toward the speaker or destination being focused on
• levar = to take → movement away from the speaker or toward another place

In this sentence, trazer is used because the idea is that the guest will bring a present to the party.

Compare:

• Ela vai trazer um presente para a festa. = She is going to bring a present to the party.
• Ela vai levar um presente para a festa. = She is going to take a present to the party.

In real usage, sometimes the distinction is a bit flexible, but trazer is the expected choice for bring.

Um means a/an, so um presente means a present.

Use um when the item is not specific or not already identified. Use o when it is specific:

• um presente = a present
• o presente = the present

So this sentence means the guest will bring a present, not a particular already-known one.

Not always. Presente can mean:

• gift / present
• present in the sense of being present or attendance, depending on context

In this sentence, because of trazer um presente, it clearly means gift.

Examples:

• Ganhei um presente. = I got a gift.
• Todos estavam presentes. = Everyone was present.

Para usually means for or to.

In para a festa, it shows destination or purpose, and in English the most natural translation is often to the party.

So:

• um presente para a festa = a present for the party / to bring to the party

In Brazilian Portuguese, pra is the very common spoken contraction of para:

• pra festa instead of para a festa in informal speech

But in the sentence you were given, para is the full standard form.

Because festa is being used with the definite article a: a festa = the party.

So:

• para + a = para a

Unlike some other Portuguese combinations, para + a is usually not written as one formal contraction in standard writing. In speech, many Brazilians say pra festa.

Compare:

• para a festa = to/for the party
• para uma festa = to/for a party

The word order is very standard:

• A convidada = subject
• vai trazer = verb phrase
• um presente = direct object
• para a festa = prepositional phrase

So the pattern is basically:

• Subject + verb + object + extra information

Portuguese word order is often similar to English in simple statements, which makes this sentence fairly straightforward.

Yes. A few natural alternatives are:

• A convidada trará um presente para a festa.
  More formal or written; simple future.

• A convidada vai levar um presente para a festa.
  Also possible, though it shifts slightly toward take rather than bring.

• A convidada vai trazer um presente pra festa.
  Very common in spoken Brazilian Portuguese.

All are understandable, but A convidada vai trazer um presente para a festa is a perfectly natural standard sentence.

A rough Brazilian Portuguese pronunciation guide would be something like:

a kõ-vee-DAH-juh vai tra-ZEHR uhm preh-ZEH-chee PAH-rah a FES-tah

A few notes:

• convidada: in many Brazilian accents, the d before a stays a normal d, but in connected speech the ending may sound softer.
• trazer: the final r is often softer than in English.
• um: the vowel is nasal.
• presente: in many Brazilian accents, the te at the end sounds like chee.
• festa: usually stressed on fes.

Pronunciation varies by region, but this gives you a useful Brazilian-style approximation.

You would change the article, noun, and sometimes the verb to match.

Male singular

• O convidado vai trazer um presente para a festa.
• The male guest is going to bring a present to the party.

Female plural

• As convidadas vão trazer um presente para a festa.
• The female guests are going to bring a present to the party.

Male or mixed plural

• Os convidados vão trazer um presente para a festa.
• The guests are going to bring a present to the party.

Notice:

• a / o / as / os change
• convidada / convidado / convidadas / convidados change
• vai / vão changes with singular vs. plural