A diretora pediu-nos para desligar o telemóvel antes da reunião.

Because Portuguese normally uses the definite article with a specific person described by a noun or title. A diretora means the director / the headmistress / the manager, depending on context.

Here, a is also feminine singular, matching diretora, which refers to a woman.

Pediu is the preterite (simple past) of pedir.

So it means asked in the sense of a completed action in the past.
The base verb is pedir = to ask / to request.

For example:

• Ela pede = she asks
• Ela pediu = she asked

Pediu-nos means asked us.

The verb is pediu = asked, and nos = us.

A useful pattern is:

pedir algo a alguém = to ask someone for something
or
pedir a alguém para fazer algo = to ask someone to do something

So in this sentence:

A diretora pediu-nos para desligar o telemóvel...
= The director asked us to turn off the mobile phone...

Here, nos refers to the people who were asked.

This is a very important feature of European Portuguese.

In affirmative main clauses, unstressed object pronouns often come after the verb, attached with a hyphen:

• pediu-nos
• disse-me
• chamaram-te

This is called enclisis.

So pediu-nos is the normal European Portuguese order here. In English, we separate the pronoun, but Portuguese often attaches it.

In European Portuguese, pediu-nos is the normal form in this sentence.

Nos pediu is much more associated with Brazilian Portuguese, where pronouns more often come before the verb.

In European Portuguese, pronouns usually move before the verb only when something triggers that position, such as:

• Não nos pediu... = She didn’t ask us...
• Já nos pediu... = She already asked us...
• Quem nos pediu isso? = Who asked us that?

So for your sentence, pediu-nos is the expected European Portuguese form.

Good question. With a full noun phrase, you often see a:

• A diretora pediu aos alunos para desligar o telemóvel.

But when that person is replaced by an unstressed object pronoun, Portuguese uses the clitic pronoun directly:

• pediu-nos

You do not say pediu a nos.

Also, nos can represent either a direct or indirect object depending on the verb. Here it is functioning as the person being asked.

Because Portuguese very often uses para + infinitive after verbs like pedir to express what someone was asked to do.

So:

pediu-nos para desligar o telemóvel
literally has the structure
asked us to turn off the mobile phone

This is completely natural.

Portuguese can also use other structures, such as:

• A diretora pediu-nos que desligássemos o telemóvel.

That version uses que + subjunctive and sounds a bit more formal or more explicit.

Yes. Para desligarmos is also possible in European Portuguese.

Portuguese has a personal infinitive, which can show who is doing the action:

• para desligar = to turn off
• para desligarmos = for us to turn off

In your sentence, para desligar is already clear because nos tells us who was asked. So the simpler infinitive works well.

Using para desligarmos can sound slightly more explicit, but it is not required here.

Yes. Telemóvel is the usual word in Portugal for mobile phone / cell phone.

In Brazilian Portuguese, the common word is celular.

So:

• Portugal: telemóvel
• Brazil: celular

Both refer to the same object, but telemóvel is the natural choice for European Portuguese.

Usually desligar o telemóvel means to switch the phone off.

If you want to say put it on silent, Portuguese would more naturally use something like:

• silenciar o telemóvel
• pôr o telemóvel em silêncio
• meter o telemóvel em silêncio (common in speech)

So the sentence you have suggests actually turning the phone off, not just muting it.

Because de + a contracts to da in Portuguese.

The expression is antes de = before, and since reunião takes the feminine article a, you get:

• antes de + a reunião → antes da reunião

This kind of contraction is very common in Portuguese:

• de + o → do
• de + a → da
• em + a → na
• a + a → à

Yes. Reunião is a feminine noun, so it uses a reunião.

That is why the contraction is da reunião:

• de + a reunião → da reunião

If the noun were masculine, you would get do instead.

The most important thing is where the stress falls.

• telemóvel: stress on mó
• reunião: stress on the final -ão

Very roughly for an English speaker:

• telemóvel ≈ tuh-luh-MOH-vel
  In European Portuguese, the first vowels are often reduced, so it can sound more compressed than this spelling suggests.

• reunião ≈ reh-oo-nee-OW̃
  The final -ão is nasal, which is a very Portuguese sound.

Also, in European Portuguese, many unstressed vowels become weaker than English speakers expect, so the words may sound shorter and more reduced in fast speech.

Yes. A very natural alternative is:

A diretora pediu-nos que desligássemos o telemóvel antes da reunião.

This uses que + imperfect subjunctive (desligássemos).

Both patterns are correct:

• pedir a alguém para + infinitive
• pedir a alguém que + subjunctive

The para + infinitive version is often simpler and very common. The que + subjunctive version can sound a bit more formal or more structured.