Minha amiga deixou de ter medo de falar na frente de todos depois de uma palestra na faculdade.

In this sentence, deixou de means stopped or no longer.

So:

• deixou de ter medo = stopped being afraid
• more literally: stopped having fear

This is a very common Portuguese structure:

• deixar de + infinitive = to stop doing something / to no longer do something

Examples:

• Ela deixou de fumar. = She stopped smoking.
• Eu deixei de sair com eles. = I stopped going out with them.

So Minha amiga deixou de ter medo... means that at one time she was afraid, but that changed.

Because in Portuguese, medo normally takes the preposition de.

So the pattern is:

• ter medo de + noun
• ter medo de + infinitive

Examples:

• Tenho medo de cachorro. = I’m afraid of dogs.
• Tenho medo de dirigir. = I’m afraid of driving.
• Ela tinha medo de falar. = She was afraid to speak / afraid of speaking.

That is why the sentence has:

• ter medo de falar

The de belongs with medo, not with falar.

Because different parts of the sentence require de for different reasons.

Let’s break it down:

• deixou de ter
  Here, deixar de + infinitive is the structure meaning to stop doing.

• medo de falar
  Here, medo de means fear of / afraid of.

• depois de uma palestra
  Here, depois de means after.

So each de has a different job. This is very normal in Portuguese, even if it sounds repetitive to an English speaker.

Na frente de todos means in front of everyone or in everyone’s presence.

Breakdown:

• em a frente de becomes na frente de
• todos = everyone / everybody / all of them, depending on context

In this sentence, falar na frente de todos means speaking where everyone is watching or listening.

It often has the sense of speaking publicly, in front of a group.

Examples:

• Ela falou na frente da turma. = She spoke in front of the class.
• Tenho vergonha de cantar na frente dos outros. = I’m embarrassed to sing in front of other people.

Not really.

For this sentence, na frente de todos is the natural choice.

• na frente de often means in front of in the sense of being before an audience or in someone’s presence
• em frente a usually refers more to physical position, like opposite or facing

Examples:

• Ela falou na frente de todos. = She spoke in front of everyone.
• O banco fica em frente à faculdade. = The bank is opposite the college.

So for public speaking, na frente de todos sounds much better.

Both can work, but they are slightly different in style.

• na frente de todos = in front of everyone / in front of all of them
• na frente de todo mundo = in front of everybody

Todo mundo is very common and natural in everyday Brazilian Portuguese.
Todos is also natural, and can sound a little more neutral or slightly more formal depending on context.

So you could also say:

• Minha amiga deixou de ter medo de falar na frente de todo mundo...

That would still sound very natural in Brazil.

Deixou is the preterite of deixar.

Here it shows a completed change in the past:

• before: she was afraid
• then something changed
• after that: she was no longer afraid

That is why the preterite fits well. It presents the stopping of the fear as a finished event.

Compare:

• Ela deixou de ter medo. = She stopped being afraid.
  Completed change.

• Ela deixava de ter medo quando praticava mais. = She would stop being afraid when she practiced more.
  More habitual or repeated idea.

In your sentence, it sounds like one significant turning point happened.

In Brazilian Portuguese, both are possible:

• Minha amiga
• A minha amiga

When a possessive comes before the noun, the definite article is often optional in Brazilian Portuguese.

So these both work:

• Minha amiga chegou.
• A minha amiga chegou.

Very general tendency:

• In Brazil, omitting the article is quite common.
• In European Portuguese, using the article is more common.

So Minha amiga sounds perfectly natural in Brazilian Portuguese.

Not exactly.

Palestra usually means:

• lecture
• talk
• speech
• sometimes presentation

It is normally a more specific event than a regular class.

So:

• uma palestra na faculdade = a lecture / talk at college

Compare:

• aula = class, lesson
• palestra = lecture, talk
• apresentação = presentation

So this sentence suggests that something about that lecture or talk helped her lose her fear of speaking in public.

By itself, it does not clearly say which one.

The phrase only means:

• after a lecture/talk at college

It could mean:

1. she attended a lecture, and after that she stopped being afraid, or
2. she gave a lecture, and after that she stopped being afraid

The sentence does not specify. Context would tell you.

If you wanted to make it clearer, you could say:

• depois de assistir a uma palestra na faculdade = after attending a lecture at college
• depois de dar uma palestra na faculdade = after giving a lecture at college

Because na faculdade means at the college/university.

It comes from:

• em + a faculdade = na faculdade

This use of em is common for location:

• na escola = at school
• no trabalho = at work
• na universidade = at the university

So:

• uma palestra na faculdade = a lecture at college

À faculdade would usually suggest motion toward it, like to the college:

• Vou à faculdade. = I’m going to the college/university.

It depends on context, and this often confuses English speakers.

In Brazilian Portuguese, faculdade can refer to higher education in general, often in ways that overlap with college or university in English.

In everyday speech:

• fazer faculdade = to go to college / attend university
• na faculdade = at college / at university

Strictly speaking, universidade is university, but in natural Brazilian usage, faculdade is very common when talking about university-level study.

So in this sentence, na faculdade would usually be translated naturally as:

• at college or
• at university

depending on the variety of English you prefer.

Yes, in many contexts that is a very natural translation.

Literally, it is:

• to speak in front of everyone

But in smoother English, depending on the situation, you might say:

• to speak in public
• to speak in front of a crowd
• to speak in front of other people

That is because the Portuguese expression focuses on the audience being present, and in many situations that matches the idea of public speaking.

A helpful way to read it is in chunks:

• Minha amiga = my friend
• deixou de ter medo = stopped being afraid
• de falar na frente de todos = of speaking in front of everyone
• depois de uma palestra na faculdade = after a lecture at college

So the structure is basically:

[subject] + [stopped being afraid] + [of doing something] + [after some event]

This kind of chunking makes long Portuguese sentences much easier to process.