Antes de anexares o ficheiro, faz uma cópia de segurança.

Because Portuguese can use the personal infinitive after prepositions like antes de.

Here, anexares is the personal infinitive of anexar for tu:

• eu anexar
• tu anexares
• ele/ela/você anexar
• nós anexarmos
• vós anexardes
• eles/elas/vocês anexarem

So Antes de anexares o ficheiro means before you attach the file, with you understood as tu.

You could also hear Antes de anexar o ficheiro when the subject is obvious, but anexares makes the subject more explicit.

Portuguese often drops subject pronouns because the verb form already shows who the subject is.

In this sentence:

• anexares shows tu
• faz is also the tu command form

So a Portuguese speaker does not need to say tu unless they want emphasis:

• Antes de anexares o ficheiro, faz uma cópia de segurança.
• Antes de tu anexares o ficheiro, faz uma cópia de segurança. ← possible, but more emphatic or marked

Yes. Faz is the affirmative imperative of fazer for tu.

So:

• faz = do / make when telling one person you address as tu to do something

Examples:

• Faz isso. = Do that.
• Faz uma cópia de segurança. = Make a backup.

This is an irregular verb, so it is worth learning separately.

Because Portuguese uses different forms for affirmative and negative commands.

For tu:

• affirmative: faz
• negative: não faças

So:

• Faz uma cópia de segurança. = Make a backup.
• Não faças isso agora. = Don’t do that now.

This difference is very common in Portuguese and especially important with irregular verbs like fazer.

Portuguese uses definite articles more often than English.

So where English might say attach file or even attach the file depending on context, Portuguese naturally says anexar o ficheiro.

Here o ficheiro sounds normal because it refers to the file being discussed in the situation. In instructions, Portuguese often uses the article in this way.

In European Portuguese, yes, ficheiro is the usual word for a computer file.

This is one clue that the sentence is from Portugal rather than Brazil.

Compare:

• European Portuguese: ficheiro
• Brazilian Portuguese: arquivo

So in Brazil, a similar sentence would more likely use arquivo.

Here anexar means to attach, especially in a digital or email context.

So anexar o ficheiro means:

• attach the file
• add the file as an attachment

It is a standard and very common verb in Portuguese for emails, forms, websites, and office instructions.

Cópia de segurança is the standard Portuguese expression for backup.

Literally, it is something like security copy or safety copy, but the natural English equivalent is backup.

In European Portuguese, this is the normal formal and neutral term:

• fazer uma cópia de segurança = make a backup
• restaurar uma cópia de segurança = restore a backup

You may also hear English-influenced backup in informal tech speech, but cópia de segurança is the standard expression.

Yes, you can.

Both are possible:

• Antes de anexares o ficheiro...
• Antes de anexar o ficheiro...

The version with anexares is more explicitly linked to tu. The version with plain anexar is a bit more neutral and can sound slightly less specific.

In practice, both are used, but the personal infinitive is very natural in Portuguese and learners should get used to seeing it.

Because the sentence begins with a subordinate clause:

• Antes de anexares o ficheiro = before attaching the file / before you attach the file

Then comes the main instruction:

• faz uma cópia de segurança

When this kind of before... clause comes first, Portuguese normally separates it with a comma:

• Antes de anexares o ficheiro, faz uma cópia de segurança.

If the order is reversed, the comma is often dropped:

• Faz uma cópia de segurança antes de anexares o ficheiro.

Yes, it strongly sounds like European Portuguese.

Main clues:

• ficheiro instead of Brazilian arquivo
• anexares and faz show a tu form, which is very common in Portugal
• the whole sentence sounds like a natural instruction in European Portuguese

A more Brazilian version might be:

• Antes de anexar o arquivo, faça uma cópia de segurança.

That version uses:

• arquivo instead of ficheiro
• faça, which fits você and is common in Brazilian formal instructions

It is a neutral instruction or practical recommendation.

It sounds like something you might read:

• in software instructions
• on a website
• in office or IT guidance
• in a help document

It is direct, but not rude. Using tu makes it sound like an instruction addressed to one user in a normal, everyday European Portuguese style.