Eu vou comprar um chapéu novo amanhã.

Yes. In Brazilian Portuguese, Eu can often be omitted because the verb form vou already shows the subject is I.

So these both work:

• Eu vou comprar um chapéu novo amanhã.
• Vou comprar um chapéu novo amanhã.

Including Eu can add emphasis, clarity, or contrast, for example:

• Eu vou comprar, não ele.
  I’m going to buy it, not him.

Vou comprar is a very common way to talk about the future in Brazilian Portuguese. It literally uses:

• vou = I go / I am going
• comprar = to buy

Together, vou comprar means I’m going to buy.

Portuguese also has a simple future form:

• comprarei = I will buy

But in everyday Brazilian Portuguese, vou comprar is usually more natural and more common in speech.

Vou is the first-person singular present tense of the verb ir (to go).

• eu vou = I go / I’m going

In this sentence, it is not mainly about physically going somewhere. It is part of the future construction:

• vou comprar = I’m going to buy

This structure is very common:

• vou estudar = I’m going to study
• vou sair = I’m going to leave
• vou viajar = I’m going to travel

Um is the indefinite article, meaning a or an.

So:

• um chapéu = a hat

It tells us the speaker is talking about one hat, not a specific known hat.

Compare:

• um chapéu = a hat
• o chapéu = the hat

In Portuguese, adjectives often come after the noun, so:

• chapéu novo = new hat

This is the most neutral and common order.

You can sometimes put the adjective before the noun:

• novo chapéu

But that can sound more literary, emphatic, or slightly different in nuance depending on the adjective and context. For a basic, everyday sentence, chapéu novo is the natural choice.

Because novo has to agree with chapéu, which is masculine singular.

Agreement in Portuguese usually works like this:

• chapéu novo = masculine singular
• camisa nova = feminine singular
• chapéus novos = masculine plural
• camisas novas = feminine plural

So the adjective changes form to match the noun.

The noun chapéu is simply a masculine word in Portuguese, so it takes:

• um chapéu
• o chapéu
• chapéu novo

There is not always a logical reason from meaning alone. Grammatical gender is something you usually learn together with the noun. A good habit is to memorize nouns with their article:

• um chapéu
• uma camisa
• um carro
• uma casa

No, it does not have to be at the end, but the end position is very natural.

These are all possible:

• Eu vou comprar um chapéu novo amanhã.
• Amanhã eu vou comprar um chapéu novo.
• Eu amanhã vou comprar um chapéu novo.

The most common and neutral choices are usually:

• Eu vou comprar um chapéu novo amanhã.
• Amanhã eu vou comprar um chapéu novo.

Putting amanhã first can give it a bit more emphasis.

In Brazilian Portuguese, chapéu is pronounced approximately like sha-PEH-o, but the final part is really a diphthong, not a fully separate English-style o.

A rough guide:

• cha sounds like sha
• péu has the stress, something like PEH-oo, blended together

Important points:

• The ch in Brazilian Portuguese usually sounds like sh
• The accent mark in chapéu shows where the stress goes

So the stress is on péu, not on cha.

Amanhã is pronounced roughly like ah-ma-NYÃ, with the last syllable nasalized.

Key points:

• The nh sounds like the ny in canyon
• The final ã is nasal, so air goes through the nose

For English speakers, the hardest part is usually that nasal ending. It is not a plain a sound.

The accent marks help show pronunciation.

In this sentence:

• chapéu has an acute accent (é), which shows the stressed vowel and helps indicate the vowel quality
• amanhã has a tilde (ã), which shows nasalization

So the accents are not optional decoration. They are part of the correct spelling and help tell you how to say the word.

Yes. That is grammatically correct.

• Eu vou comprar um chapéu novo amanhã. = I’m going to buy a new hat tomorrow.
• Eu comprarei um chapéu novo amanhã. = I will buy a new hat tomorrow.

However, in Brazilian Portuguese, vou comprar is much more common in everyday conversation. Comprarei can sound more formal, more written, or sometimes more emphatic.

Yes, this sentence is fairly close to English word order:

• Eu = I
• vou comprar = am going to buy
• um chapéu novo = a new hat
• amanhã = tomorrow

So the structure is:

Subject + future expression + object + time expression

That makes this a very learner-friendly sentence. The main differences from English are:

• Portuguese often uses adjective-after-noun order: chapéu novo
• The future is often formed with ir + infinitive: vou comprar