Minha mãe deixou dois guardanapos na mesa e esquentou água na chaleira para o café.

Because minha has to agree with the noun being possessed, not with the speaker.

• mãe is feminine singular
• so the possessive must also be feminine singular: minha

Compare:

• minha mãe = my mother
• meu pai = my father

In Brazilian Portuguese, possessives can appear with or without a definite article.

So both are possible:

• Minha mãe
• A minha mãe

In Brazil, both sound natural, though usage varies by region, style, and speaker. In a sentence like this, Minha mãe is completely normal.

Here, deixou means something like left, put, or set down.

It is the preterite form of deixar, so it means she left/put.

That verb is very common and can have several meanings depending on context, such as:

• leave
• let / allow
• stop / give up
• leave behind

In this sentence, because of dois guardanapos na mesa, the meaning is clearly left/placed on the table.

Because guardanapo is a masculine noun.

So the number has to match:

• dois guardanapos = two napkins

If the noun were feminine, you would use duas:

• duas xícaras = two cups

Na is a contraction:

• em + a = na

Since mesa is feminine, em a mesa becomes na mesa.

Also, Portuguese often uses em where English uses on, in, or at depending on the situation. So:

• na mesa literally comes from in the table
• but in natural English it means on the table

They are both in the preterite, the normal tense for completed actions in the past.

So the sentence presents two finished actions:

• she left two napkins on the table
• she heated water in the kettle

This is the usual tense for telling what happened in sequence.

If the sentence were about repeated or habitual past actions, Portuguese would more likely use the imperfect:

• deixava
• esquentava

Not necessarily.

Esquentar means to heat or to warm up. It does not automatically mean boil.

So esquentou água means she heated some water. Maybe it boiled, maybe it just got hot.

If you want to be more specific about boiling, you could say:

• ferveu a água = boiled the water
• colocou a água para ferver = put the water on to boil

Because Portuguese often omits the article with a mass noun when speaking in a general or indefinite way.

So:

• esquentou água = heated water / heated some water

If you say:

• esquentou a água

that usually sounds more like the water, meaning specific water already known from the context.

Both are possible, but água without an article is very natural here.

Here it means in the kettle.

Again, na is em + a, because chaleira is feminine:

• na chaleira = in the kettle

Portuguese em covers several English prepositions, so you have to rely on context.

Also, chaleira is specifically a kettle, the thing used to heat water. That is different from:

• bule = coffee pot / teapot

It shows purpose: the water was heated for the coffee.

In natural English, depending on context, that could be:

• for the coffee
• to make coffee
• for coffee

In this sentence, it most likely means the water was heated to prepare coffee.

Also, café by itself usually means coffee, not breakfast.
Breakfast is café da manhã.

Yes. In spoken Brazilian Portuguese, para o is very often reduced to pro.

So both are possible:

• para o café
• pro café

Pro is extremely common in speech and informal writing.
For neutral or more careful writing, para o is the safest choice.

Because both verbs have the same subject.

Portuguese, like English, often avoids repeating the subject when it is already clear:

• Minha mãe deixou dois guardanapos na mesa e esquentou água...

The subject minha mãe applies to both deixou and esquentou.

Repeating it would still be grammatical, but it would usually sound unnecessary:

• Minha mãe deixou dois guardanapos na mesa e minha mãe esquentou água...

A rough Brazilian pronunciation is:

• mãe ≈ my, but with a nasal vowel
• chaleira ≈ sha-LAY-ra

A few useful sound notes:

• ch sounds like sh
• lh is a palatal sound, roughly similar to ly for many English speakers
• mãe is only one syllable, and the vowel is nasal

So:

• mãe ≈ nasal my
• chaleira ≈ sha-LAY-ra