A professora pediu que eu abrisse a câmera, mas eu fiquei de terminar a apresentação primeiro.

Because after pedir que in Portuguese, the verb in the next clause normally goes in the subjunctive.

• pediu = asked / requested
• que eu abrisse = that I open / that I should open

So:

• A professora pediu que eu abrisse a câmera = The teacher asked me to turn on the camera

Why not the other forms?

• eu abri is the preterite indicative: I opened. That would state a completed fact, not the content of the request.
• eu abrir is the personal infinitive, which is not used after pedir que in this structure.

This is a very common pattern:

• Ela pediu que eu esperasse. = She asked me to wait.
• O professor pediu que eles estudassem mais. = The teacher asked them to study more.

Abrisse is the imperfect subjunctive of abrir.

Here is the relevant part of the conjugation:

• eu abrisse
• você/ele/ela abrisse
• nós abríssemos
• vocês/eles/elas abrissem

In this sentence, it does not mean past in the same way an English past tense does. After a past-tense main verb like pediu, Portuguese often uses the imperfect subjunctive in the subordinate clause.

So:

• A professora pediu ... → past
• que eu abrisse ... → the requested action, expressed in the subjunctive

It is best understood as part of the grammar pattern, not translated word-for-word as I was opening or I opened.

Yes. In Brazilian Portuguese, pedir para + infinitive is also very common.

So both of these are natural:

• A professora pediu que eu abrisse a câmera
• A professora pediu para eu abrir a câmera

They are very close in meaning.

A rough comparison:

• pedir que + subjunctive can sound a bit more formal or more traditionally grammatical
• pedir para + infinitive is extremely common in everyday Brazilian Portuguese

Both are useful and natural to learn.

In this sentence, ficar de + infinitive means something like:

• to be supposed to
• to be left to
• to promise/agree to
• to still have to

So:

• eu fiquei de terminar a apresentação primeiro

means that the speaker had committed to, was supposed to, or still needed to finish the presentation first.

This expression is common in Brazilian Portuguese. Examples:

• Fiquei de ligar para ela. = I said I would call her / I still had to call her.
• Ele ficou de mandar o arquivo. = He said he would send the file.
• Nós ficamos de conversar depois. = We agreed to talk later.

The exact English translation depends on context.

Because the verb ficar in this meaning requires the preposition de:

• ficar de + infinitive

So the correct structure is:

• fiquei de terminar
• ficou de enviar
• ficamos de conversar

Without de, the sentence would sound wrong in this meaning.

This is something you mostly have to learn as a fixed pattern.

Because after ficar de, Portuguese uses the infinitive, not a subjunctive clause.

Compare the two structures in the sentence:

1. pediu que eu abrisse

   • pedir que + subjunctive

2. fiquei de terminar

   • ficar de + infinitive

So the grammar changes because the expression changes.

That is why you get:

• A professora pediu que eu abrisse...
• eu fiquei de terminar...

not:

• eu fiquei de que terminasse... ❌

Primeiro means first, and here it modifies the idea of terminar a apresentação.

So the meaning is:

• I was supposed to finish the presentation first
• I needed to finish the presentation before doing that

In other words, the speaker is saying the teacher asked for the camera to be turned on, but the speaker had to finish the presentation before doing it.

You can think of the implied sequence like this:

1. finish the presentation
2. then open/turn on the camera

Because there are two different clauses, and each has its own subject:

1. A professora pediu que eu abrisse a câmera
2. mas eu fiquei de terminar a apresentação primeiro

Portuguese often repeats the subject pronoun for clarity or emphasis, especially when a new clause starts.

In many cases, Portuguese can omit eu, because the verb ending already shows the subject:

• A professora pediu que eu abrisse a câmera, mas fiquei de terminar a apresentação primeiro.

That version is also natural.

Including eu in the second clause can make it a bit clearer or more contrastive:

• but I had to finish the presentation first

Portuguese uses definite articles much more often than English does.

So a câmera literally means the camera, but in context it may correspond to English the camera or just my camera / camera depending on the situation.

In online-class context, abrir a câmera usually means:

• turn on the camera
• switch on your webcam

Even if English might say turn on your camera without stressing the, Portuguese naturally uses the article:

• abrir a câmera
• ligar a câmera

The same thing happens with:

• a professora = the teacher
• a apresentação = the presentation

Literally, yes: abrir means to open. But in Brazilian Portuguese, in digital/classroom contexts, abrir a câmera often means:

• turn on the camera
• activate the webcam

This is one of those expressions where the literal meaning and the practical meaning are a bit different.

Depending on the context, Brazilians may also say:

• ligar a câmera = turn on the camera
• abrir a câmera = open/turn on the camera
• abrir o microfone = unmute / turn on the microphone

So you should learn the expression as a natural tech/classroom phrase.

Because Portuguese often uses the definite article before nouns where English would not.

So:

• A professora pediu...

is a very normal way to say:

• The teacher asked...

In some contexts, Brazilian Portuguese also uses articles before job titles or roles even when English would simply say teacher, doctor, mom, and so on.

You may also hear:

• A Ana chegou. = Ana arrived.
• O professor falou isso. = The teacher said that.

This is a very common feature of spoken Brazilian Portuguese.

Mas means but.

It introduces a contrast:

• the teacher asked the speaker to turn on the camera
• but the speaker had to finish the presentation first

So the sentence is showing a conflict between:

• the teacher’s request
• the speaker’s immediate obligation or plan

This is a straightforward coordinating conjunction, just like English but.

No, not in this sentence.

Portuguese ficar has many meanings, which can confuse learners. For example:

• ficar = stay
• ficar = become
• ficar com = keep / be with
• ficar de + infinitive = be supposed to / agree to / still have to

Here, fiquei de terminar is specifically the expression ficar de + infinitive. It does not mean:

• I ended up finishing
  or
• I became finishing

So it is important to treat ficar de as a set phrase here.

Not necessarily, but it suggests a delay.

The sentence says:

• the teacher asked the speaker to turn on the camera
• but the speaker had to finish the presentation first

This strongly implies:

• the speaker did not turn it on immediately

However, the sentence alone does not tell us whether the speaker turned it on later. That would depend on the wider context.

So the safest reading is:

• the speaker postponed opening the camera until after finishing the presentation