Learn Hardcore Portuguese (Portugal): Antes do exame, fico em silêncio durante um minuto, respirando fundo e organizando as ideias. - Before the exam, I stay silent for a minute, breathing deeply and organizing my ideas.

Portuguese often drops subject pronouns when they are clear from the verb ending.
The verb fico is 1st person singular of ficar, so it already means “I stay / I remain”.

Eu fico em silêncio… = I stay in silence…
Normally you just say Fico em silêncio…; eu is optional unless you want to emphasize I.

So “I” is understood from fico, even though it isn’t written.

Why is it “Antes do exame” and not “Antes de exame” or “Antes o exame”?

The basic structure is antes de + noun.
When de comes before a masculine singular noun with o, they contract:

antes de + o exame → antes do exame

So:

Antes do exame = Before the exam.
Antes de um exame = Before an exam (any exam).
Antes de estudar = Before studying (before + verb; no article here).

“Antes o exame” is incorrect, and “antes de exame” sounds incomplete/unnatural in this context.

Why is it “fico em silêncio” and not “estou em silêncio” or “sou silencioso”?

ficar here means “to stay / remain / be for a while”.
- Fico em silêncio = I stay quiet / I remain silent (for that period).
estar em silêncio can work, but it sounds more like describing your state at a given moment:
Estou em silêncio agora = I am silent now.
sou silencioso means “I am a quiet person (by nature)”, a permanent characteristic.

In this context (a temporary state before the exam), fico em silêncio is the most natural.

Why is the verb tense “fico” (present) if this is a routine I do before exams?

Portuguese uses the simple present a lot for:

Habits and routines:
Antes de dormir, leio um livro. = Before sleeping, I read a book.
Todos os dias, corro. = Every day, I run.

So Fico em silêncio… is “I (usually) stay silent… / I stay silent (whenever I’m in that situation).”
The present tense naturally covers habitual actions in Portuguese, just like in English: “I breathe deeply.”

What exactly does “em silêncio” mean, and could I say “fico silencioso” instead?

em silêncio literally means “in silence”, and idiomatically “silent / quietly”. It focuses on not speaking / making noise.

Fico em silêncio = I remain silent / I keep quiet.

silencioso is an adjective, more like “quiet / silent (by character or style)”:

um aluno silencioso = a quiet student.

You could say fico silencioso, but fico em silêncio is more idiomatic here and more clearly “I don’t talk” rather than “I am a quiet-type person.”

Is “durante um minuto” necessary? Could I just say “um minuto”?

durante emphasizes the duration:

durante um minuto = for one minute.

You can say:

Fico em silêncio um minuto – also acceptable and common.
Fico em silêncio durante um minuto – slightly more explicit/formal about the time span.

Both are fine; durante is not strictly required, but it’s very natural with time expressions.

What is “respirando” grammatically? How is it different from “respiro”?

respirando is the gerúndio (gerund) of respirar – like “breathing” in English.

In this sentence, it works as a “while doing …” phrase:

fico em silêncio…, respirando fundo e organizando as ideias
≈ I stay silent while breathing deeply and organizing my thoughts.

If you said:

Respiro fundo e organizo as ideias.
you’d be using full finite verbs: I breathe deeply and I organize my thoughts.

Both structures are correct; the gerund version sounds more like a description of what you do during that minute, a bit smoother and more continuous.

What does “fundo” mean in “respirando fundo”? Why not “profundamente”?

Here fundo is used adverbially and means “deeply”:

respirar fundo = to take a deep breath / to breathe deeply.

You could say respirar profundamente, which is more literal/formal for “breathe deeply”, but in everyday speech respirar fundo is more common and more natural in European Portuguese.

So:

respirando fundo = breathing deeply.

Why is it “organizando as ideias” and not “as minhas ideias”?

In Portuguese, possessives are often omitted when the owner is obvious from context.

as ideias here clearly means my ideas, because the subject is I.
Saying as minhas ideias is also correct, just a bit more explicit.

Very common patterns:

Lavo as mãos. = I wash (my) hands.
Fechei os olhos. = I closed (my) eyes.

So organizando as ideias is natural and fully understood as “organizing my thoughts.”

Why are “respirando fundo” and “organizando as ideias” connected with “e” but still both depend on fico?

Both gerunds (respirando, organizando) describe simultaneous actions performed by the same subject (I) during that time:

Fico em silêncio, [respirando fundo] e [organizando as ideias].

The e just links the two ongoing actions. You can think:

I stay silent, (while) breathing deeply and (while) organizing my thoughts.

The subject “I” is the same for both gerunds, so it doesn’t need to be repeated.

What is the role of the comma before “respirando fundo”? Could I remove it?

The comma separates the main clause from the descriptive gerund phrase:

Antes do exame, fico em silêncio durante um minuto, [respirando fundo e organizando as ideias].

This gerund phrase explains how or in what manner you stay in silence.

You’ll usually see a comma before such a trailing gerund phrase in Portuguese.
Writing it without the comma (…um minuto respirando fundo e…) is possible but less clear; with the comma, the structure is nicer and more standard.

Could I say “Antes do exame, respiro fundo e organizo as ideias durante um minuto.” instead? Is the meaning the same?

Yes, that sentence is perfectly correct:

Antes do exame, respiro fundo e organizo as ideias durante um minuto.

The meaning is very close, but there is a nuance:

Fico em silêncio…, respirando fundo e organizando as ideias.
Focuses first on the state (I stay silent) and then describes what you do during that state.
Respiro fundo e organizo as ideias…
Lists two actions you perform, a bit more like steps.

Both would be natural in European Portuguese; the original version is slightly more descriptive of the whole “minute of silence” as one state.