Antes da reunião online, eu vou revisar a apresentação com calma.

Because de + a usually contracts to da in Portuguese.

• antes de + a reunião → antes da reunião

This is very common with prepositions and articles:

• de + o → do
• de + a → da
• em + a → na
• em + o → no

So antes da reunião online means before the online meeting.

When antes means before, it is normally followed by de.

Examples:

• antes da reunião = before the meeting
• antes de sair = before leaving

A very useful pattern is:

• antes de + noun
• antes de + infinitive

So in your sentence:

• antes da reunião online = before the online meeting

And compare:

• Antes de estudar, eu tomo café. = Before studying, I drink coffee.

The phrase Antes da reunião online is an introductory time expression placed at the beginning of the sentence. In Portuguese, it is very common to separate that kind of opening phrase with a comma.

So:

• Antes da reunião online, eu vou revisar a apresentação com calma.

This comma is natural and helps readability. You may sometimes see short introductory phrases without a comma, but here the comma is standard and clear.

Yes, it can often be omitted.

Portuguese is a pro-drop language, which means subject pronouns are often unnecessary because the verb ending already shows who the subject is.

So both are possible:

• Eu vou revisar a apresentação com calma.
• Vou revisar a apresentação com calma.

Both mean I’m going to review the presentation calmly / carefully.

Why include eu?

• for emphasis
• for clarity
• for contrast with someone else

For example:

• Eu vou revisar a apresentação, mas ela vai preparar os gráficos.

Vou revisar is the very common spoken way to talk about the future in Brazilian Portuguese.

• vou revisar = I’m going to review / I will review
• revisarei = I will review

Both are correct, but they feel different:

• vou revisar → more natural in everyday speech
• revisarei → more formal, more written, sometimes more distant or deliberate

In Brazil, people very often prefer ir + infinitive for future meaning:

• vou estudar
• vamos sair
• ela vai chegar cedo

So your sentence sounds very natural.

In this sentence, revisar usually means to review, to check over, or to go through carefully.

That matters because English revise can mean different things depending on the variety of English:

• In American English, revise often means edit/change/improve
• In British English, revise can also mean study again / review

Portuguese revisar often means:

• check
• review
• proofread
• inspect

So here vou revisar a apresentação most naturally means:

• I’m going to review the presentation
• I’m going to go over the presentation

It may or may not imply making changes.

Because apresentação is a feminine singular noun, so it takes the feminine singular definite article a.

• a apresentação = the presentation

Gender and article agreement are important in Portuguese:

• o relatório = the report
• a apresentação = the presentation

If you wanted to say a presentation in a non-specific sense, you might use:

• uma apresentação

But in your sentence, a apresentação suggests a specific presentation that both speaker and listener know about.

Com calma literally means with calm, but in natural English it usually means:

• calmly
• carefully
• without rushing
• at ease

So:

• vou revisar a apresentação com calma

can mean:

• I’m going to review the presentation carefully
• I’m going to go over the presentation without rushing

This is a very common expression in Portuguese.

Other examples:

• Fala com calma. = Speak calmly / Take it easy.
• Vamos fazer isso com calma. = Let’s do this carefully / without rushing.

In Portuguese, adjectives often come after the noun, although placement can vary depending on the adjective and the effect wanted.

So:

• reunião online = online meeting

This is the normal order. Portuguese commonly keeps words like online after the noun:

• aula online = online class
• curso online = online course
• evento online = online event

You may also hear alternatives like:

• reunião virtual

Yes. Online is very common in Brazilian Portuguese and is widely understood in everyday speech and writing.

Examples:

• reunião online
• curso online
• loja online

You might also see:

• on-line in older or more formal writing
• virtual in some contexts

But online is extremely natural in modern Brazilian Portuguese.

Yes. Grammatically, online describes reunião.

So the most direct reading is:

• before the online meeting

It does not mean:

• before getting online for the meeting

If you wanted to express that other idea more explicitly, you would probably say something like:

• Antes de entrar na reunião online...
• Antes de me conectar para a reunião...

So in your sentence, online modifies reunião.

Yes, it is very natural. The sentence structure is:

• Antes da reunião online = time phrase
• eu vou revisar = subject + future expression
• a apresentação = direct object
• com calma = manner expression

Portuguese allows some flexibility, but this version sounds normal and clear.

Possible variations:

• Eu vou revisar a apresentação com calma antes da reunião online.
• Vou revisar a apresentação com calma antes da reunião online.

These are also natural. The original version puts emphasis first on when the action will happen.

A natural Brazilian pronunciation would often sound roughly like this:

• Antes da reunião online, eu vou revisar a apresentação com calma.

Some helpful notes:

• antes: the final s is usually pronounced like s
• da: short and unstressed
• reunião: the ending -ão is nasal
• eu vou: often flows together smoothly
• revisar: final r is often softer in many Brazilian accents
• apresentação: another nasal -ão
• com calma: often sounds connected in natural speech

A very rough English-friendly approximation might be:

• AHN-tchis da heh-oo-nee-OWN on-LY-nee, eh-o VOH heh-vee-ZAR a ah-preh-zehn-ta-SOWN kong KAWL-ma

But that is only approximate, since Portuguese sounds, especially nasal vowels, do not match English exactly.

Yes, but some positions sound more natural than others.

Your sentence:

• Antes da reunião online, eu vou revisar a apresentação com calma.

This is very natural.

Other possible placements:

• Eu vou revisar a apresentação com calma antes da reunião online.
• Com calma, eu vou revisar a apresentação antes da reunião online.

That last version gives more emphasis to com calma and may sound more marked depending on context.

In everyday speech, the original placement is simple and natural.