No domingo, eu vou estudar português de manhã e descansar à tarde.

No = em + o.

• o domingo = Sunday
• em o domingo contracts to no domingo

In this sentence, no domingo means on Sunday.

Just domingo can also appear in Portuguese in some contexts, but no domingo is a very common and natural way to say on Sunday, especially when talking about a specific Sunday.

Useful contrast:

• no domingo = on Sunday / this Sunday / that Sunday depending on context
• aos domingos = on Sundays, every Sunday

Because No domingo is a time expression placed at the beginning of the sentence.

That comma is very natural in writing because it separates the opening time phrase from the main sentence:

• No domingo, eu vou estudar...

It is similar to English:

• On Sunday, I’m going to study...

In casual writing, some people may omit it, but using the comma here is standard and clear.

Eu vou estudar is the very common ir + infinitive future, literally I am going to study.

In Brazilian Portuguese, this structure is extremely common in everyday speech for future actions.

So:

• eu vou estudar = I’m going to study / I will study
• eu estudarei = simple future, more formal or less common in conversation

Both are correct, but vou + infinitive sounds more natural in most spoken Brazilian Portuguese.

You can often omit eu.

Portuguese is a language where the verb form often shows the subject clearly:

• vou already tells you it is I

So both are possible:

• Eu vou estudar português...
• Vou estudar português...

Including eu can add:

• emphasis
• contrast
• clarity

In this sentence, eu is perfectly fine, but it is not strictly necessary.

In Portuguese, names of languages are normally not capitalized.

So:

• português
• inglês
• espanhol

This is different from English, where you write Portuguese, English, Spanish with capitals.

So estudar português is correct, not estudar Português, unless it starts a sentence.

The accent in português shows the stressed syllable and helps distinguish pronunciation.

• por-tu-GUÊS

That ê tells you the stress falls at the end and that the vowel has a specific sound.

Accent marks in Portuguese are important because they are part of the correct spelling, not optional pronunciation hints.

These are fixed time expressions that you should mostly learn as chunks:

• de manhã = in the morning
• à tarde = in the afternoon
• à noite = at night / in the evening

They do not all use the same preposition, so it is best not to translate word by word from English.

So in this sentence:

• estudar português de manhã = study Portuguese in the morning
• descansar à tarde = rest in the afternoon

À is the contraction of a + a. This is called crase in Portuguese.

Here:

• a = a preposition
• a tarde = the feminine noun phrase the afternoon
• together: à tarde

So à tarde is the standard expression meaning in the afternoon.

You will also see this in:

• à noite
• às vezes
• à esquerda

The accent is important: a and à are not the same in writing.

Because one vou can govern both infinitives when they are joined by e:

• eu vou estudar português de manhã e descansar à tarde

This means:

• I’m going to study Portuguese in the morning and rest in the afternoon

Repeating vou is possible, but not necessary:

• eu vou estudar português de manhã e vou descansar à tarde

That version is also correct, but the original is smoother and more natural here.

Because after vou in the ir + infinitive future structure, the main verb stays in the infinitive.

So:

• vou estudar
• vou descansar
• vou comer
• vou viajar

This is one of the most useful future patterns in Portuguese:

• subject + ir (conjugated) + infinitive

Usually, for general time-of-day expressions, Portuguese prefers the fixed forms:

• de manhã
• à tarde
• à noite

So in this sentence, de manhã and à tarde are the natural choices.

Na manhã and na tarde are possible in other contexts, but they usually sound more specific, like during the morning of a particular day/event rather than the general adverbial expression in the morning / in the afternoon.

For example:

• Na manhã de domingo, choveu. = On Sunday morning, it rained.

But for a routine plan like this sentence, de manhã and à tarde are the normal choices.

This is an important difference:

• no domingo = on Sunday, one specific Sunday
• aos domingos = on Sundays, regularly / every Sunday

Examples:

• No domingo, eu vou estudar português. = one Sunday
• Aos domingos, eu estudo português. = every Sunday / on Sundays

So the sentence you have is talking about a specific plan, not a habit.

Yes, somewhat.

The original sentence is very natural:

• No domingo, eu vou estudar português de manhã e descansar à tarde.

You could also say:

• Eu vou estudar português de manhã e descansar à tarde no domingo.

But putting No domingo first is very common because it sets the time frame immediately.

Portuguese often moves time expressions around for emphasis or style, but the original order is clear and natural.