Antes da apresentação, as minhas mãos começam a tremer, mas eu respiro fundo.

Because da is the normal contraction of de + a.

• antes de = before
• a apresentação = the presentation

So:

• antes de a apresentação → contracts to antes da apresentação

This kind of contraction is very common in Portuguese:

• de + o = do
• de + a = da
• de + os = dos
• de + as = das

So antes da apresentação is the natural standard form.

In Portuguese, especially in European Portuguese, possessives often appear with a definite article:

• as minhas mãos = my hands
• literally: the my hands

This is completely normal in Portuguese grammar. With body parts and personal belongings, this structure is especially common.

So a learner should get used to patterns like:

• o meu livro = my book
• a minha casa = my house
• as minhas mãos = my hands

In some situations, especially in other varieties or styles, the article may be omitted, but in European Portuguese, using the article is very common and usually sounds more natural.

After the verb começar, Portuguese normally uses a + infinitive to mean to begin/start doing something.

So:

• começar a tremer = to start trembling
• começam a tremer = they start trembling

This is a very common pattern:

• começo a trabalhar = I start working
• ela começa a rir = she starts laughing
• nós começamos a falar = we begin to speak

So the a is not the article here. It is part of the verbal structure começar a + infinitive.

Because after começar a, the next verb stays in the infinitive.

In English, we also often do something similar:

• start trembling
• begin to tremble

Portuguese uses:

• começar a tremer

Here:

• começam is the conjugated verb
• tremer stays in the infinitive

You do not conjugate both verbs. So not começam tremem, but começam a tremer.

Because mãos is plural, so the verb must also be plural.

• a mão = the hand
• as mãos = the hands

Since as minhas mãos is plural, the verb must be começam:

• a minha mão começa = my hand starts
• as minhas mãos começam = my hands start

This is just normal subject-verb agreement.

Yes, and the meaning is slightly different.

• as minhas mãos tremem = my hands tremble / are trembling
• as minhas mãos começam a tremer = my hands start to tremble

The version with começam a emphasizes the moment when the trembling begins. It gives a stronger sense of reaction right before the presentation.

So both are possible, but the original sentence is a bit more vivid.

Yes, it can often be omitted.

Portuguese is a pro-drop language, which means the subject pronoun is often left out because the verb ending already shows who the subject is:

• respiro already means I breathe

So both are possible:

• mas eu respiro fundo
• mas respiro fundo

Including eu can add emphasis or contrast. In this sentence, eu helps create a contrast:

• my hands start trembling, but I breathe deeply

So eu is not required, but it sounds natural if you want to stress I.

Respirar fundo is a very common expression meaning to breathe deeply or to take a deep breath.

So:

• respiro fundo = I breathe deeply / I take a deep breath

Literally, fundo means deep. In this expression, Portuguese uses fundo where English often uses an adverb like deeply.

Both of these are possible in Portuguese, but they are not equally natural in all contexts:

• respiro fundo = very common, natural, idiomatic
• respiro profundamente = grammatically possible, but less idiomatic here

So learners should treat respirar fundo as a set expression.

Yes, it is in the present tense, and in Portuguese that can express either:

1. something happening now, or
2. something that generally happens

In this sentence, the most natural interpretation is often a habitual or typical reaction:

• Before the presentation, my hands start trembling, but I breathe deeply.

That sounds like something that usually happens in that situation.

Portuguese present tense is very flexible, just like English present tense can sometimes be:

• I get nervous before presentations.
• My hands start shaking, but I take a deep breath.

Because antes da apresentação is an introductory time expression placed at the beginning of the sentence.

The comma helps separate that opening phrase from the main clause:

• Antes da apresentação, = Before the presentation,
• as minhas mãos começam a tremer...

This is similar to English punctuation. The comma is natural and helps readability, though punctuation rules can vary a little by style.

There is also a comma before mas, which is normal because mas means but and joins two contrasting clauses.

Yes, both words contain nasal vowels, which are very important in Portuguese.

mãos

This has a nasal sound similar to ow̃.
It is not pronounced like a plain English mouse without the -se. The vowel is nasal, and the -s is pronounced like sh in standard European Portuguese when it comes at the end of the word before a pause:

• mãos ≈ mow̃sh

apresentação

The ending -ção is very common in Portuguese and is pronounced roughly like:

• -sãw̃ in European Portuguese

So apresentação ends with a nasal sound too.

A helpful thing to notice is this very common spelling pattern:

• -ção → often corresponds to English -tion
• informação, situação, apresentação

If you want, a rough learner-friendly pronunciation of the whole sentence in European Portuguese is:

• Antes da apresentação, ash minhash mãwsh começam a tremer, mash eu respiro fundo.

That is only approximate, but it helps highlight the nasal vowels and the sh sound at the end of as, mãos, and mas in European Portuguese pronunciation.

Yes, this sentence works in European Portuguese, and it would also be understood in Brazil. But there are a few differences in style and pronunciation.

Things that are especially natural in European Portuguese:

• as minhas mãos with the article
• the pronunciation of final s as sh in many contexts
• a more reduced pronunciation of unstressed vowels

In Brazilian Portuguese:

People might also say:

• Antes da apresentação, minhas mãos começam a tremer, mas eu respiro fundo.

The article before the possessive is less consistently used in Brazil, depending on region and style.

Also, pronunciation differs a lot:

• mãos and apresentação still have nasal vowels
• but the overall rhythm and vowel quality are different from Portugal

So grammatically the sentence is fine for both, but it sounds especially at home in European Portuguese.

Mas means but. It introduces contrast.

In the sentence, the contrast is:

• my hands start trembling
• but I breathe deeply

So although the speaker feels nervous physically, they respond by calming themselves.

This is one of the most common Portuguese conjunctions:

• Quero ir, mas estou cansado. = I want to go, but I’m tired.
• Ela estudou, mas o teste foi difícil. = She studied, but the test was difficult.

Yes. Depending on context, apresentação can mean several related things, such as:

• a presentation
• a performance
• an introduction
• a showing/appearance

In this sentence, because of antes da apresentação and the nervous reaction, presentation is the most likely meaning.

But in another context, it could be something like:

• a apresentação da peça = the performance of the play
• a apresentação do novo funcionário = the introduction of the new employee

So the exact meaning depends on context, even though the basic idea is always something being presented.

Here are the main ones:

• antes = before
• apresentação = presentation
• mão = hand
• começar = to begin / to start
• tremer = to tremble / to shake
• mas = but
• eu = I
• respirar = to breathe
• fundo = deep / deeply in this expression

This is useful because in Portuguese you often need to recognise the infinitive or singular dictionary form:

• mãos → mão
• começam → começar
• respiro → respirar