Escrevi o roteiro antes da vinheta.

Escrevi is the 1st person singular form of the pretérito perfeito (the simple past / preterite) of escrever.

• escrever = to write
• escrevi = I wrote

In this sentence, it refers to a completed action in the past.

Examples:

• Escrevi o roteiro ontem. = I wrote the script yesterday.
• Escrevi e depois revisei. = I wrote it and then revised it.

So escrevi is not I was writing; it is I wrote.

Portuguese often omits subject pronouns when the verb form already makes the subject clear.

So instead of:

• Eu escrevi o roteiro antes da vinheta.

you can simply say:

• Escrevi o roteiro antes da vinheta.

Because escrevi clearly means I wrote, eu is optional.

You might include eu if you want:

• emphasis
• contrast
• clarity

For example:

• Eu escrevi o roteiro, não ela. = I wrote the script, not her.

Portuguese uses definite articles much more often than English.

So o roteiro literally means the script, and using the article here sounds natural in Portuguese.

In English, you might sometimes say:

• I wrote the script
• or even I wrote script material in some contexts

But in Portuguese, with a specific thing like this, o roteiro is the normal choice.

A few points:

• o = masculine singular definite article
• roteiro is a masculine noun
• so: o roteiro

Because in Portuguese, de + a normally contracts to da.

So:

• de + a = da

That means:

• antes da vinheta = before the intro/jingle/title card
• literally: before of-the vinheta

This kind of contraction is very common:

• de + o = do
• de + a = da
• de + os = dos
• de + as = das

Examples:

• antes do filme = before the movie
• depois da aula = after the class

Yes. The basic structure is antes de = before.

When de is followed by an article, it contracts:

• antes de + a vinheta → antes da vinheta
• antes de + o almoço → antes do almoço

So the pattern is:

• antes de + noun/infinitive
• antes do / da / dos / das when there is an article

Examples:

• antes de sair = before leaving
• antes do almoço = before lunch
• antes da reunião = before the meeting

So in your sentence:

• antes da vinheta = before the vinheta

In Brazilian Portuguese, vinheta can have a few related meanings depending on context, especially in media.

Common meanings include:

• a short intro
• a jingle
• a bumper
• a title/opening segment
• a short audiovisual identifier for a TV/radio/program brand

So in a media context, vinheta is often that brief branded intro you hear or see before a segment starts.

That is why roteiro and vinheta fit well together in the same sentence: both are common in TV, radio, video, or production contexts.

Yes. Portuguese allows some flexibility in word order.

The original sentence:

• Escrevi o roteiro antes da vinheta.

You could also say:

• Antes da vinheta, escrevi o roteiro.

Both are correct. The difference is mainly focus:

• Escrevi o roteiro antes da vinheta.
  More neutral; starts with the action.

• Antes da vinheta, escrevi o roteiro.
  Gives more emphasis to the time relationship: before the intro.

Both sound natural.

This is a very common question.

• escrevi = I wrote
  A completed action in the past

• escrevia = I was writing / I used to write
  An ongoing, repeated, habitual, or background action in the past

Compare:

• Escrevi o roteiro antes da vinheta.
  I wrote the script before the intro.
  → the writing is seen as completed

• Eu escrevia o roteiro enquanto a vinheta tocava.
  I was writing the script while the intro was playing.
  → ongoing past action

So in your sentence, escrevi is used because the action is presented as a finished event.

Because vinheta is a noun, so you use antes de + noun:

• antes da vinheta = before the intro

If you want to say before it starts or before starting, then you would use antes de + infinitive or clause.

Examples:

• antes de começar a vinheta = before the intro starts
• antes de começar = before starting

So:

• antes da vinheta = before the intro itself
• antes de começar a vinheta = before the intro begins

They are related, but not identical in structure.

Roteiro most commonly means script in film, TV, theater, video, and similar contexts.

But it can also mean:

• an outline
• a plan
• an itinerary
• a route
• a guide

Examples:

• roteiro de filme = film script
• roteiro de viagem = travel itinerary
• roteiro da apresentação = presentation outline

So the exact meaning depends on context. In your sentence, it most likely means script, especially because of vinheta, which suggests a media/production context.