A investigação começou na oficina.

A is the feminine singular definite article, meaning the.

So:

• a investigação = the investigation
• uma investigação = an investigation

Portuguese uses articles more regularly than English, so where English might sometimes omit the, Portuguese often keeps it.

In Portuguese, every noun has a grammatical gender, usually masculine or feminine. Investigação is a feminine noun.

That is why it takes:

• a investigação (not o investigação)

A useful clue is the ending -ção, which is very often feminine:

• a investigação
• a informação
• a situação
• a organização

So if you see a noun ending in -ção, it is very often feminine.

Começou is the 3rd person singular of the verb começar in the pretérito perfeito (simple past / preterite).

So it means:

• he/she/it started
• began

In this sentence, the subject is a investigação, which is grammatically 3rd person singular, so:

• A investigação começou = The investigation started

Other forms of começar in the same tense:

• eu comecei = I started
• tu começaste = you started
• ele/ela começou = he/she started
• nós começámos = we started
• vocês/eles/elas começaram = you/they started

The accent in começou helps show the correct stress and vowel quality.

• começou is stressed on the last syllable: co-me-ÇOU
• The ending -ou is a common past-tense ending in Portuguese

It also helps distinguish pronunciation from other forms of the verb. In European Portuguese, the stress pattern is very important, so accents are not optional decoration—they guide pronunciation.

Because na is a contraction of:

• em + a = na

So:

• na oficina = in the workshop / in the garage

This kind of contraction is extremely common in Portuguese:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

Examples:

• no carro = in the car
• na casa = in the house
• nos livros = in the books
• nas escolas = in the schools

So em a oficina is not the normal form; na oficina is the correct one.

Em is used for location: in, at, inside, depending on context.

Here, na oficina tells you where the investigation started.

Compare:

• na oficina = in/at the workshop
• para a oficina = to the workshop
• à oficina = to the workshop / at the workshop in some specific structures, but not the normal choice here for simple location

Because this sentence is describing the place where something happened, em is the natural preposition.

In European Portuguese, oficina often means:

• workshop
• repair shop
• garage, especially a mechanic’s garage

So the exact English translation depends on context.

For example:

• oficina de automóveis = car repair shop / garage
• oficina de artista = artist’s studio/workshop
• oficina in a school or cultural setting can also mean a workshop activity

In this sentence, workshop or garage could both be possible depending on the wider context.

Usually no, not in this sentence.

Portuguese often uses an article with places or nouns when referring to a specific location:

• na oficina = in the workshop / in the garage

If you said em oficina, it would sound unnatural in most ordinary contexts. The version with the article is the normal one.

Yes. Portuguese word order is somewhat flexible.

The neutral order is:

• A investigação começou na oficina.

But you could also say:

• Na oficina, a investigação começou.

This gives more emphasis to the location, a bit like:

• In the workshop, the investigation began.

The original version is the most straightforward and neutral.

A simple pronunciation guide is:

• A investigação começou na oficina.
• roughly: uh invesh-ti-guh-SOWN koo-meh-SOH nah oo-fee-SEE-nuh

A few important points for European Portuguese:

• investigação ends with a nasal sound: -ção
• ç in começou sounds like s
• ou in começou is pronounced like a closed o sound
• unstressed vowels are often reduced in European Portuguese, much more than in Brazilian Portuguese

A more approximate stressed breakdown:

• a inves-ti-ga-ÇÃO
• co-me-ÇOU
• na o-fi-CI-na

Yes, in many contexts you could say:

• A investigação iniciou-se na oficina.
• A investigação iniciou na oficina. (less standard in many contexts)
• A investigação começou na oficina.

But começou is very natural and common.

A small nuance:

• começar = to start / begin
• iniciar = to initiate / begin, often slightly more formal

So começou is usually the safest and most everyday choice.

Because Portuguese normally does not need an explicit subject pronoun when the subject noun is already there.

The subject is:

• A investigação

So after that, Portuguese simply uses the verb:

• A investigação começou

You do not need a separate word for it.

If you translated word-for-word from English as something like A investigação ela começou, that would usually be unnecessary or unnatural here.

Not always. Investigação can mean:

• investigation
• inquiry
• research, depending on context

In Portugal, investigação is also commonly used for academic research:

• investigação científica = scientific research

But in a sentence like this, especially with na oficina, it may sound more like an investigation or inquiry. The exact English word depends on the context you are given.