Eu preciso relatar o furto.

Yes. In Brazilian Portuguese, eu is often optional because preciso already shows that the subject is I.

So all of these can work:

• Eu preciso relatar o furto.
• Preciso relatar o furto.

Including eu can add emphasis, clarity, or contrast, but it is not required in most situations.

Because precisar works differently depending on what comes after it.

• precisar + infinitive verb = to need to do something

  • Preciso relatar o furto. = I need to report the theft.

• precisar de + noun = to need something

  • Preciso de ajuda. = I need help.
  • Preciso de um advogado. = I need a lawyer.

So in your sentence, relatar is a verb, so de is not used.

No. Here preciso is from the verb precisar, meaning to need.

This can confuse learners because preciso can also be an adjective meaning precise / accurate.

Compare:

• Eu preciso relatar o furto. = I need to report the theft.
• O horário não é preciso. = The time is not precise.

So the meaning depends on the grammar and context.

After precisar meaning to need to, the next verb normally stays in the infinitive.

Structure:

• precisar + infinitive

Examples:

• Preciso sair. = I need to leave.
• Preciso falar com você. = I need to talk to you.
• Preciso relatar o furto. = I need to report the theft.

This is very similar to English need to + verb.

It is correct, but it can sound a bit formal or specific depending on the context.

Relatar means something like:

• to report
• to relate
• to describe what happened

It often suggests giving an account of the facts.

Other common verbs you might hear are:

• denunciar o furto = report it to the authorities / make a complaint
• comunicar o furto = notify / inform
• registrar a ocorrência or registrar um boletim de ocorrência = officially file a police report

So Eu preciso relatar o furto is understandable and correct, but in a real police-station situation, something like Preciso registrar um boletim de ocorrência may sound more natural.

Portuguese often uses definite articles more than English does.

Here o furto means the theft, referring to the specific theft being discussed.

Using the article makes the noun sound more complete and natural in many contexts.

Compare:

• relatar o furto = report the theft
• relatar um furto = report a theft

If both speaker and listener already know which theft is meant, o furto is the natural choice.

This is a very important vocabulary distinction in Portuguese.

• furto = theft without direct violence or threat
• roubo = robbery, involving violence or threat

So if someone quietly steals your phone when you are not looking, that is usually furto.
If someone threatens you and takes your phone, that is roubo.

English learners often translate both simply as theft or robbery, but Portuguese makes this distinction more clearly.

It sounds mostly neutral to somewhat formal.

• Eu preciso is neutral and common.
• relatar is a little more formal than some everyday alternatives.

In casual speech, a Brazilian might also say:

• Preciso contar o que aconteceu. = I need to say what happened.
• Preciso denunciar o furto.
• Preciso registrar a ocorrência.

So your sentence is correct and natural enough, but it leans slightly toward official or formal language.

Both are common, but they are slightly different in tone.

• Preciso relatar o furto. = I need to report the theft.
• Tenho que relatar o furto. = I have to report the theft.

Preciso often sounds a little more neutral or personal.
Tenho que can sound a bit more like obligation or necessity.

In many real situations, either one would work.

A rough Brazilian Portuguese pronunciation is:

eh-ooh preh-SEE-zoo heh-lah-TAR oo FOOR-too

A few helpful notes:

• Eu often sounds like two quick vowels together.
• preciso is stressed on -ci-: pre-CI-so
• relatar is stressed on the last syllable: re-la-TAR
• furto is stressed on fur-: FUR-to
• In many Brazilian accents, the r in relatar and furto is not like the English r

You do not need to pronounce every word separately in a stiff way. In normal speech, the sentence flows together smoothly.

You can, if you want to make the listener explicit:

• Preciso relatar o furto à polícia. = I need to report the theft to the police.

That is perfectly correct.

But if you are already at a police station or clearly speaking to the authorities, Portuguese often leaves that part understood:

• Preciso relatar o furto.

So both are fine. The shorter version is often enough in context.