A voz da Ana treme quando ela fala em público, mas depois deixa de tremer.

In European Portuguese, it is very common to use the definite article before a person’s name: a Ana, o João.

So:

• de + a Ana → da Ana
• A voz da Ana = Ana’s voice / the voice of Ana

Without the article, de Ana is not impossible in all contexts, but da Ana sounds much more natural in everyday Portuguese from Portugal.

Portuguese usually expresses possession with de rather than with an apostrophe-style structure like English.

So English:

• Ana’s voice

normally becomes Portuguese:

• a voz da Ana

This is one of the most basic and natural ways to show possession in Portuguese.

Treme is the present indicative of the verb tremer (to tremble, to shake).

Conjugation:

• eu tremo
• tu tremes
• ele/ela/você treme

Here, A voz da Ana treme means Ana’s voice trembles / is trembling, depending on context. Portuguese often uses the simple present where English might use either:

• trembles
• is trembling

Both are possible.

• quando ela fala em público
• quando fala em público

Portuguese often drops the subject pronoun because the verb ending already shows the person. However, ela may be included:

• for clarity
• for emphasis
• to avoid ambiguity

In this sentence, ela helps make it very clear that we are talking about Ana.

Em público means in public or in front of other people / an audience.

It is a fixed expression:

• falar em público = to speak in public
• estar em público = to be in public

Notice that Portuguese uses em, not something like para o público here.

Because the sentence describes something that generally happens to Ana.

• A voz da Ana treme quando ela fala em público
  = Her voice trembles when she speaks in public.

This is a habitual or general truth, so Portuguese uses the present tense:

• treme
• fala
• deixa

English often does the same in this kind of sentence.

Depois means afterwards, later, or then.

In this sentence:

• mas depois deixa de tremer

it means something like:

• but afterwards it stops trembling
• but then it stops trembling

So the sentence describes two stages:

1. her voice trembles at first
2. later, it stops

No. Deixar de + infinitive is a very common structure meaning:

• to stop doing something
• to cease doing something
• sometimes to no longer do something

So:

• deixa de tremer = stops trembling

Examples:

• Deixei de fumar. = I stopped smoking.
• Ela deixou de estudar. = She stopped studying.

So here deixa is not the everyday meaning to leave. It is part of the expression deixar de + infinitive.

Because after deixar de, Portuguese normally uses an infinitive:

• deixar de tremer
• deixar de falar
• deixar de chover

So the repetition is completely natural. Portuguese does not usually replace the second verb with something shorter in this structure.

The sentence literally follows this pattern:

• [subject] + deixa de + [infinitive]

Grammatically, the subject is still A voz da Ana.

So the full structure is:

• A voz da Ana treme ... mas depois deixa de tremer.

The thing that trembles is the voice, and the thing that later stops trembling is also the voice.

Even though Ana is mentioned in the middle clause (quando ela fala em público), the main subject of the whole sentence remains A voz da Ana.

Portuguese often prefers a voz da Ana instead of a sua voz when it wants to be clear.

Why?

Because sua can be ambiguous. It might mean:

• her
• his
• your (depending on variety and context)

So a voz da Ana is clearer and very natural.

Those would change the meaning slightly.

• treme = states the fact simply
• está a tremer = emphasizes that the trembling is happening at that moment
• fica a tremer = can suggest ends up trembling or starts remaining in that state

The original sentence uses treme, which is the most neutral and straightforward choice for a general description.

Yes, it fits European Portuguese very naturally, especially because of things like:

• the article before the name: da Ana
• the general phrasing

Also, in European Portuguese, if you wanted a progressive form, you would typically say:

• está a tremer
• está a falar

whereas Brazilian Portuguese often prefers:

• está tremendo
• está falando

But the sentence as written is correct and natural in Portugal.

In European Portuguese, treme is pronounced approximately like TREH-muh, but the final vowel is often very reduced.

A rough guide:

• tre- sounds like treh
• -me is not a strong mee sound; it is weaker, more like muh or a very reduced vowel

Also, European Portuguese tends to reduce unstressed vowels more than Brazilian Portuguese, so the ending may sound less clear to English-speaking learners.

Yes. In this sentence, quando can be understood as:

• when
• whenever

Because the sentence describes a repeated or typical situation:

• Her voice trembles whenever she speaks in public.

That is a very natural interpretation.

Mas means but.

It introduces a contrast:

• first: her voice trembles
• then: it stops trembling

So mas links two opposite or contrasting parts of the situation.

Yes, para de tremer is also possible and means stops trembling.

However, there is a slight difference in style:

• parar de + infinitive = very common, direct, everyday
• deixar de + infinitive = also very common, sometimes a little more neutral or formal depending on context

So these are both natural:

• mas depois para de tremer
• mas depois deixa de tremer

The original version is perfectly good Portuguese.