O Pedro tocou a buzina porque o portão estava fechado.

In European Portuguese, it is very common to use the definite article before a person’s first name:

• O Pedro
• A Maria

This does not mean the Pedro in a strange English sense. It is just normal Portuguese usage in many contexts.

So:

• O Pedro tocou a buzina. = Pedro honked the horn.

You can also hear just Pedro without the article, but O Pedro is extremely natural in Portugal.

Tocou is the pretérito perfeito simples of tocar.

Here it describes a completed action in the past:

• tocou = honked, sounded, pressed

So O Pedro tocou a buzina means that Pedro did the action once or as a finished event.

Compare:

• tocou = he honked / he sounded the horn
• tocava = he used to honk / he was honking

Yes, tocar has several meanings, and this is very common in Portuguese.

It can mean:

• to touch
• to play an instrument
• to ring / sound
• in expressions like tocar a buzina, to honk or to sound the horn

So in this sentence:

• tocar a buzina = to honk the horn

This is a set expression you should learn as a chunk.

Buzina is a feminine noun, so it takes the feminine singular article a:

• a buzina = the horn

In this sentence, it refers to the vehicle horn.

A learner should notice that Portuguese often uses the definite article where English may or may not use one. Here, both languages use it naturally:

• the horn
• a buzina

Not exactly.

• porta = door
• portão = gate, usually a larger exterior gate

So o portão estava fechado means:

• the gate was closed

This suggests Pedro was probably outside a property, garage, driveway, or entrance blocked by a gate.

Estava fechado describes a state or condition in the past:

• estava fechado = was closed

It does not focus on the action of closing the gate. It focuses on the result or situation at that moment.

Compare:

• O portão estava fechado. = The gate was closed.
  
  • state/condition
• Alguém fechou o portão. = Someone closed the gate.
  
  • action
• O portão foi fechado. = The gate was closed.
  
  • passive, focusing more on the action/event of being closed

In your sentence, the important idea is the reason Pedro honked: the gate was in a closed state.

Because fechado agrees with o portão, which is masculine singular.

Agreement in Portuguese matters:

• o portão fechado = masculine singular
• a porta fechada = feminine singular
• os portões fechados = masculine plural
• as portas fechadas = feminine plural

So:

• o portão estava fechado

is correct because portão is masculine.

Because here it means because, introducing a reason:

• porque = because

So:

• Pedro tocou a buzina porque o portão estava fechado.

Portuguese has several similar forms, which often confuse learners:

• porque = because
• porquê = the reason / why (a noun)
• por que = why / for which reason
• por quê = why? at the end of a question

In your sentence, only porque is correct.

Portuguese often drops subject pronouns like ele, ela, eles, because the verb ending already gives information. But here the subject is not a pronoun carried over from before; it is a new noun phrase:

• first clause subject: O Pedro
• second clause subject: o portão

So you need to say o portão because it introduces what was closed.

You could not just say:

• O Pedro tocou a buzina porque estava fechado.

That would sound incomplete or unclear, because we would ask: what was closed?

Yes, that is also correct.

Both of these are natural:

• O Pedro tocou a buzina porque o portão estava fechado.
• Porque o portão estava fechado, o Pedro tocou a buzina.

The first version is more neutral and straightforward.
The second puts more emphasis on the reason.

So Portuguese allows flexibility here, just like English:

• Pedro honked because the gate was closed.
• Because the gate was closed, Pedro honked.

A rough learner-friendly pronunciation is:

• O Pedro tocou a buzina porque o portão estava fechado.
• u PEDru tu-KOH a bu-ZEE-na purk' u pur-TAWN iS-TA-va fi-SHA-du

A few useful points for European Portuguese:

• o often sounds closer to u in unstressed position
• de in Pedro is not pronounced like strong English day
• ão in portão is nasal
• estava in European Portuguese is often reduced in fast speech
• fechado has ch pronounced like sh

This is only an approximation, but it helps you hear what is happening.