Learn Hardcore Portuguese (Portugal): Eu também fico envergonhado quando falo demasiado depressa em público. - I also get embarrassed when I speak too fast in public.

Using Eu adds a tiny bit of emphasis on I (especially in contrast, like I also…), but in everyday speech it’s very common just to say Também fico envergonhado….

Why is também in the middle (Eu também fico…)? Could it go somewhere else?

Yes, também can move, but the meaning/emphasis changes slightly:

Eu também fico envergonhado… – neutral and most common: I also get embarrassed…
Também eu fico envergonhado… – more emphatic or formal/literary, like I, too, get embarrassed…
Eu fico também envergonhado… – possible, but sounds a bit heavier or marked in European Portuguese.

For everyday European Portuguese, Eu também fico… or simply Também fico… is the most natural choice.

Why is fico used instead of estou? What’s the difference between fico envergonhado and estou envergonhado?

fico envergonhado = I get / I become embarrassed (a change of state)
- ficar often means to become, to get in this kind of structure.
estou envergonhado = I am embarrassed (describing your current state, not the change).

In your sentence, you’re talking about what happens when you speak too fast in public: you become embarrassed. So fico envergonhado is the natural choice.

Is envergonhado an adjective? Does it change for gender and number?

Yes, envergonhado is an adjective and it agrees with the subject:

Eu fico envergonhado – man speaking
Eu fico envergonhada – woman speaking
Nós ficamos envergonhados – group of men / mixed group
Nós ficamos envergonhadas – group of women

So you must match -o / -a / -os / -as to who is getting embarrassed.

Could I say Tenho vergonha instead of Fico envergonhado?

You can, but it changes the nuance slightly:

Fico envergonhado quando… – I get embarrassed when… (focus on the reaction/change of state).
Tenho vergonha quando… – literally I have shame when…, used as I feel ashamed/embarrassed when… (focus on the feeling).

Both are natural in European Portuguese. Fico envergonhado sounds a bit more like an automatic reaction that kicks in.

Why is it quando falo and not quando estou a falar?

Both are possible, but:

quando falo demasiado depressa em público
– simple present; describes a general, habitual situation: when I (tend to) speak too fast in public.
quando estou a falar demasiado depressa em público
– continuous aspect; focuses more on the action while I am (in the process of) speaking too fast in public.

In European Portuguese, the simple present (quando falo) is very commonly used for these general cause–effect statements, so that version is the most typical.

Could I use a future tense like quando falar or quando falar em público?

Not here. In European Portuguese:

Quando falo… (when I speak…) is used for general/habitual situations.
Quando falar… (when I speak [in the future]…) is used for a specific future event or condition, e.g.
Quando falar em público amanhã, vou ficar envergonhado.
When I speak in public tomorrow, I’ll get embarrassed.

Your original sentence is a general statement about yourself, so quando falo is correct.

What is the difference between demasiado depressa, muito depressa and depressa demais?

demasiado depressa – too quickly (more neutral/standard in Portugal).
muito depressa – very quickly (not necessarily too quickly).
depressa demais – also too quickly, more informal/colloquial-style; perfectly normal in speech.

So:

To keep the “too fast” idea in European Portuguese, demasiado depressa or depressa demais are both fine.
muito depressa softens the meaning to just very fast.

Why depressa and not rápido? Are they interchangeable?

depressa is an adverb and is very common in European Portuguese:

Falo depressa. – I speak fast/quickly.

rápido is originally an adjective (rápida conversa = quick chat), but it’s also widely used as an adverb in everyday speech:

Falo rápido. – also I speak fast.

In Portugal, depressa sounds a bit more neutral/standard as an adverb; rápido is also correct but slightly more colloquial in this adverbial use.
In Brazil, rápido and rápido demais are very common.

Does demasiado always mean too in a negative sense?

Yes, demasiado typically expresses excess, like too much / too many / too + adjective/adverb, usually with a negative or problematic idea:

Como demasiado. – I eat too much.
É demasiado caro. – It’s too expensive.
Falo demasiado depressa. – I speak too fast.

For positive emphasis (really, very), Portuguese normally uses muito, not demasiado.

Why is it em público and not no público or para o público?

em público = in public (in front of other people, not in private).
no público literally = in the audience; you’d use this when talking about the audience, not about yourself.
para o público = for the public / for the audience (focusing on directing something to them).

In this sentence, the idea is in public, in front of people, so em público is the natural expression.

Could I change the word order, for example Em público, eu também fico envergonhado quando falo demasiado depressa?

Yes. Word order in Portuguese is somewhat flexible, especially for emphasis:

Eu também fico envergonhado quando falo demasiado depressa em público. – neutral order.
Em público, eu também fico envergonhado quando falo demasiado depressa. – puts emphasis on in public at the start.
Quando falo demasiado depressa em público, eu também fico envergonhado. – emphasises the when-clause.

All are grammatically correct; the main difference is what you highlight first.

Why is there no comma before quando in the original sentence?

In Portuguese, you usually:

do not put a comma before a short subordinate clause that comes after the main clause:
Eu também fico envergonhado quando falo demasiado depressa em público.

You do use a comma when the subordinate clause comes first:

Quando falo demasiado depressa em público, eu também fico envergonhado.

So the original punctuation is correct and follows a standard pattern.

Is the sentence natural and typical for European Portuguese, or does it sound Brazilian?

The sentence is perfectly natural for European Portuguese, and actually:

demasiado depressa is more typical of Portugal than Brazil (where you’d more often hear muito rápido or rápido demais).
The overall structure Eu também fico envergonhado quando falo… is common in both varieties.

So this is a very good model sentence specifically for Portuguese from Portugal.