Começamos, contanto que o doador de sangue se sinta bem.

Because contanto que triggers the subjunctive in Portuguese.

In this sentence, contanto que means provided that / as long as, and it introduces a condition. After expressions like that, Portuguese normally uses the subjunctive to show something uncertain, dependent, or conditional.

So:

• se sinta bem = feels well / is feeling well in a conditional sense
• se sente bem would be the indicative, which does not fit naturally after contanto que

A similar pattern appears in:

• Vou, contanto que ele venha. = I’ll go, provided that he comes.

Contanto que means provided that, as long as, or on condition that.

It introduces a requirement that must be true for the main action to happen.

So in this sentence, the idea is:

• Começamos = We begin / We’ll begin
• contanto que... = provided that...
• o doador de sangue se sinta bem = the blood donor feels well

Other similar expressions in Portuguese are:

• desde que = as long as / provided that
• a não ser que = unless
• caso = in case

The verb here is sentir-se bem, which means to feel well.

So:

• sentir = to feel
• sentir-se = to feel oneself / to feel

In Portuguese, many expressions about physical or emotional state are commonly reflexive:

• Ele se sente cansado. = He feels tired.
• Ela se sente melhor. = She feels better.

That is why the sentence uses:

• o doador de sangue se sinta bem

The se refers back to o doador de sangue.

Because in Portuguese, começamos can be either:

• present tense: we begin / we start
• preterite: we began / we started

The form is the same in spelling.

Which meaning is intended depends on context. In this sentence, because of the conditional phrase contanto que..., the most natural reading is usually something like:

• We’ll begin / We begin, provided that...

In real-life Brazilian Portuguese, speakers often use the present tense to talk about an immediate future action:

• Começamos agora. = We’re starting now.
• Saio amanhã. = I’m leaving tomorrow.

So even though começamos is grammatically present/preterite in form, here it most likely refers to a present or near-future action.

Portuguese often uses the definite article more often than English does.

So:

• o doador de sangue = the blood donor

Even when English might omit an article in some contexts, Portuguese frequently keeps it.

In this sentence, o points to a specific donor relevant to the situation, not just blood donors in general.

Compare:

• O paciente está pronto. = The patient is ready.
• O médico chegou. = The doctor arrived.

Yes, literally it is donor of blood, but the natural English translation is blood donor.

This is a very common structure in Portuguese:

• banco de sangue = blood bank
• doação de sangue = blood donation
• exame de sangue = blood test

Portuguese often uses de + noun where English uses a noun as an adjective.

The comma separates the main clause from the conditional clause introduced by contanto que.

So the structure is:

• Começamos = main clause
• contanto que o doador de sangue se sinta bem = condition

This comma helps readability and is very natural in writing.

You may also see similar punctuation with other linking expressions:

• Vamos, desde que haja tempo.
• Aceito, contanto que você me ajude.

Yes, both can be possible, but they are not exactly the same.

• se sinta bem = feels well
• esteja bem = is well / is doing well

In this sentence, se sinta bem emphasizes the donor’s own feeling or physical sensation. That makes a lot of sense in a medical or donation context.

Examples:

• Espero que ele se sinta bem. = I hope he feels well.
• Espero que ele esteja bem. = I hope he is well.

The first is a bit more about how he feels; the second is a bit broader.

Because the normal order is:

subject + reflexive pronoun + verb + complement

So:

• o doador de sangue = subject
• se = reflexive pronoun
• sinta = verb
• bem = complement/adverb

That gives:

• o doador de sangue se sinta bem

Portuguese pronoun placement has rules, but in a clause introduced by que, putting se before the verb is standard and expected.

Yes, it is correct and used, but in everyday Brazilian Portuguese, desde que is often more common in casual speech.

So these are very similar:

• Começamos, contanto que o doador de sangue se sinta bem.
• Começamos, desde que o doador de sangue se sinta bem.

Both mean roughly We’ll begin, as long as the blood donor feels well.

Contanto que can sound a little more formal or explicit, depending on context.

Here bem means well, not good.

That is because it goes with the verb sentir-se:

• sentir-se bem = to feel well

If you wanted good as an adjective, Portuguese would usually use bom/boa, but that would not fit this structure:

• Ele está bem. = He is well.
• Ele se sente bem. = He feels well.
• Ele é bom. = He is good.

So in this sentence, bem is the natural word.

Yes. That is a very natural translation.

Depending on context, possible English versions include:

• We begin, provided that the blood donor feels well.
• We start, as long as the blood donor is feeling well.
• We’ll begin, provided that the blood donor feels well.

The exact English tense can vary because Portuguese often uses the present tense for immediate future actions.

Both are possible, but they feel a little different.

• Começamos can be used for a planned or immediate future in spoken Portuguese.
• Começaremos is the simple future: we will begin

So:

• Começamos, contanto que... sounds more conversational and immediate.
• Começaremos, contanto que... sounds a bit more formal or explicit.

Brazilian Portuguese often prefers the present tense for near-future situations, especially in speech.