Perdi o meu pente, por isso pedi outro pente à minha irmã.

They are both in the pretérito perfeito simples, which is the normal tense in Portuguese for a completed action in the past.

• perdi = I lost
• pedi = I asked for / I requested

So the sentence describes two finished actions:

1. I lost the comb.
2. Because of that, I asked my sister for another one.

For English speakers, this usually corresponds to the simple past.

In European Portuguese, it is very common to use the definite article before a possessive:

• o meu pente
• a minha irmã
• o teu livro

So o meu pente is the normal European Portuguese pattern.

A learner should know this difference:

• European Portuguese: usually o meu, a minha, os meus, etc.
• Brazilian Portuguese: the article is often omitted, so meu pente is more common there.

In this sentence, o meu pente sounds natural and standard for Portugal.

Because pente is a masculine noun in Portuguese, so it takes masculine words with it:

• o pente
• meu pente
• outro pente

Portuguese noun gender does not always match the word ending. Even though pente ends in -e, it is still masculine.

You usually just have to learn the gender with the noun:

• o pente = the comb

Por isso means so, therefore, or for that reason.

It connects the two ideas:

• Perdi o meu pente → first event
• por isso pedi outro pente → consequence

It is a very common linking expression in Portuguese.

Other similar connectors include:

• então = so / then
• por causa disso = because of that
• por essa razão = for that reason

In this sentence, por isso is a very natural choice.

Here, à marks the person you asked.

The verb pedir works like this:

• pedir alguma coisa a alguém
• to ask someone for something

So in this sentence:

• outro pente = the thing requested
• à minha irmã = the person asked

That means:

• pedi outro pente à minha irmã = I asked my sister for another comb

The à is a contraction of:

• a
  • a minha irmã → à minha irmã

The accent is important because it shows this contraction.

Portuguese organizes pedir differently from English.

In English, we often say:

• I asked my sister for another comb

In Portuguese, the most natural structure is:

• I asked another comb to my sister in terms of grammar structure, even though that sounds wrong in English

So:

• pedir + thing requested + a + person
• pedi outro pente à minha irmã

This is very common with pedir.

A good pattern to remember is:

• Pedi ajuda ao professor.
• Pedimos informação à rececionista.
• Ela pediu dinheiro ao pai.

Outro pente is the most natural way to say another comb here.

In Portuguese, outro often works without um:

• Quero outro.
• Preciso de outra caneta.
• Pedi outro pente.

You can sometimes hear um outro, but it often has a slightly different feel, more like a different one or one other. In many everyday cases, especially in European Portuguese, outro pente is the simpler and more idiomatic choice.

Yes, you could leave it out if the meaning is clear.

The full sentence says:

• Perdi o meu pente, por isso pedi outro pente à minha irmã.

But Portuguese can also say:

• Perdi o meu pente, por isso pedi outro à minha irmã.

That is perfectly natural because outro can stand alone when the noun is understood.

The repeated pente just makes the sentence a bit more explicit and clear, which is often useful in learning materials.

Yes, sometimes.

• Perdi o pente = I lost the comb
• Perdi o meu pente = I lost my comb

In many situations, Portuguese can use the definite article where English uses a possessive, especially if ownership is obvious from context. But o meu pente is clearer and more explicit.

So:

• Perdi o pente can be natural if everyone already knows it is your comb.
• Perdi o meu pente stresses ownership more clearly.

This is a very common confusion for English speakers because English uses ask for both ideas.

Portuguese usually separates them:

• pedir = to ask for / request
• perguntar = to ask a question

So:

• Pedi outro pente à minha irmã = I requested another comb from my sister
• Perguntei à minha irmã onde estava o pente = I asked my sister where the comb was

In your sentence, the speaker is requesting an object, so pedir is the correct verb.

Yes, but it becomes a bit more advanced.

For example:

• Perdi-o, por isso pedi outro à minha irmã.

Here:

• -o = it, replacing o pente

You could also replace à minha irmã with an indirect object pronoun in some contexts:

• Perdi o meu pente, por isso pedi-lhe outro.

Here:

• lhe = to her

So the full sentence can be reduced, but the original version is clearer for learners:

• Perdi o meu pente, por isso pedi outro pente à minha irmã.

It is very natural here because por isso introduces the result of the first clause.

• Perdi o meu pente, por isso pedi outro pente à minha irmã.

The comma helps separate:

1. the cause or first event
2. the consequence

In normal writing, this punctuation is standard and clear. Without the comma, the sentence would look less natural.