Apesar de estar cansado, eu vou trabalhar hoje.

Apesar de means despite or in spite of. It introduces a contrast:

• Apesar de estar cansado = Despite being tired
• eu vou trabalhar hoje = I’m going to work today

So the whole sentence shows that being tired does not stop the speaker from going to work.

Because apesar normally takes the preposition de.

So you say:

• apesar de + noun
• apesar de + infinitive
• apesar de + clause (with some structure changes, depending on the sentence)

In this example:

• estar cansado = to be tired
• apesar de estar cansado = despite being tired

The de is required here.

Portuguese uses estar for temporary states and conditions, and ser for more permanent characteristics or identity.

Here, cansado is a temporary condition, so:

• estar cansado = to be tired

Using ser cansado would sound wrong here, because it would suggest something like being a tiring person or would simply be unnatural in this context.

The adjective must agree with the person being described.

• cansado = masculine singular
• cansada = feminine singular

Since the speaker says eu, we do not know the gender from eu alone. The form cansado tells us the speaker is male, or is being referred to with the masculine form.

If the speaker were female, it would be:

• Apesar de estar cansada, eu vou trabalhar hoje.

Because Portuguese often uses the infinitive without repeating the subject when the subject is understood from context.

In this sentence, estar cansado refers to the same person as eu later in the sentence. So Portuguese does not need to say something like eu estar cansado here.

That is completely natural:

• Apesar de estar cansado... = Despite being tired...

It works much like English being tired or although I’m tired, depending on how you translate it.

Yes, it could be omitted.

Portuguese is a pro-drop language, which means subject pronouns are often left out when the verb already makes the subject clear.

So both are natural:

• Apesar de estar cansado, eu vou trabalhar hoje.
• Apesar de estar cansado, vou trabalhar hoje.

The version with eu adds a little emphasis or clarity. A speaker might include it to sound more explicit, contrast themselves with someone else, or simply by personal style.

Vou trabalhar is the structure ir + infinitive, which is a very common way to talk about the near future in Portuguese.

• vou = I go / I am going
• trabalhar = to work

Together:

• vou trabalhar = I’m going to work / I will work

Portuguese also has a simple future tense:

• trabalharei

But in everyday Brazilian Portuguese, vou trabalhar is much more common in normal conversation.

Usually, no. Here trabalhar means to work, not to go to work as a destination phrase by itself.

So:

• vou trabalhar hoje usually means I’m going to work today in the sense of I will work today

If you specifically want to emphasize going to the workplace, Portuguese often says:

• vou ao trabalho = I’m going to work (to the workplace)
• vou para o trabalho = I’m going to work / to work

But in many contexts, English I’m going to work today and Portuguese vou trabalhar hoje match very naturally.

Hoje means today, and yes, its position can move.

In your sentence:

• eu vou trabalhar hoje

This is very natural. But you could also hear:

• Hoje eu vou trabalhar.
• Eu hoje vou trabalhar.
  (possible, but less neutral and often more marked)

The most common positions are:

• at the beginning for emphasis on today
• at the end in a neutral statement

So the original sentence sounds very normal.

Yes, that is a good alternative, but the grammar changes.

• Apesar de estar cansado, eu vou trabalhar hoje.
• Embora eu esteja cansado, eu vou trabalhar hoje.

Both mean roughly Although I’m tired, I’m going to work today.

The difference is that:

• apesar de is followed here by de + infinitive
• embora is followed by a clause with the subjunctive
  • eu esteja

So you cannot simply swap one for the other word-for-word without changing the structure.

The first part, Apesar de estar cansado, is an introductory contrast phrase. The comma helps separate that introductory element from the main clause:

• Apesar de estar cansado, eu vou trabalhar hoje.

This is standard and natural punctuation in Portuguese.

It is neutral and completely natural in both speech and writing.

• apesar de is common and standard
• vou trabalhar is very common in everyday Brazilian Portuguese
• the whole sentence sounds normal, not slangy and not overly formal

So it works well in conversation, messages, and ordinary writing.

In Brazilian Portuguese, trabalhar is commonly pronounced roughly like:

• trah-bah-LYAR
  or more loosely for English speakers:
• tra-ba-LHAR, with the lh sounding like the lli in million for many learners

A few helpful pronunciation notes:

• lh is a special Portuguese sound, not a plain English l
• the final r in Brazilian Portuguese is often pronounced like an English h sound in many accents:
  • trabalhar may sound roughly like trabalháh

This varies by region, but the important thing is to recognize that lh and final r may not sound the way an English speaker expects from spelling.

Yes. That is very common.

Examples:

• Apesar do cansaço, eu vou trabalhar hoje.
  = Despite the tiredness, I’m going to work today.

• Apesar da chuva, eu vou trabalhar hoje.
  = Despite the rain, I’m going to work today.

Notice that de combines with articles:

• de + o = do
• de + a = da

So apesar de is very flexible: it can be followed by a noun phrase or, as in your sentence, by an infinitive phrase.