Minha mãe não gosta de pepino, mas adora salada de repolho.

Because minha has to agree with mãe, the thing being possessed. Since mãe is a feminine singular noun, you use minha.

Compare:

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

So the possessive changes to match the noun, not the speaker.

Yes. In Brazilian Portuguese, both minha mãe and a minha mãe are possible.

• Minha mãe não gosta...
• A minha mãe não gosta...

In Brazil, using the article before a possessive is very common, but leaving it out is also completely natural in many contexts. The version in your sentence sounds normal and idiomatic.

Because gostar is a verb that normally takes the preposition de.

So you say:

• gostar de música
• gostar de chocolate
• gostar de pepino

This is different from English, where to like does not need a preposition. In Portuguese, you should learn gostar as gostar de.

Because the two verbs work differently.

• gostar → needs de
• adorar → does not need a preposition

So:

• Ela gosta de pepino.
• Ela adora salada de repolho.

This is very common in Portuguese: different verbs require different sentence patterns, even if their meanings seem similar in English.

Here, the speaker is talking about those foods in a general sense, not about one specific cucumber or one specific cabbage salad.

So:

• não gosta de pepino = doesn’t like cucumber / cucumbers in general
• adora salada de repolho = loves cabbage salad in general

If you wanted to be more specific, you might use an article or another determiner:

• do pepino que comprei ontem
• da salada de repolho da sua tia

Mas means but. It connects two contrasting ideas:

• she doesn’t like one thing
• she adores another thing

It works very much like English but:

• Ele é alto, mas tímido.
• Quero sair, mas estou cansado.

Yes. Adorar is stronger than gostar.

A rough scale would be:

• não gostar de = not like
• gostar de = like
• adorar = love / really love / adore

So this sentence creates a strong contrast: she doesn’t like one food, but she really loves another.

Literally, salada de repolho means cabbage salad.

• salada = salad
• repolho = cabbage
• de repolho = of cabbage / made with cabbage

Depending on the context, it can refer to something similar to coleslaw, but it does not always have to mean the exact same dish an English speaker imagines. It simply tells you the main ingredient is cabbage.

Yes. In Portuguese, de + noun is a very common way to describe material, ingredient, type, or content.

Examples:

• suco de laranja = orange juice
• bolo de chocolate = chocolate cake
• sopa de legumes = vegetable soup
• salada de repolho = cabbage salad

So de repolho tells you what kind of salad it is.

Because the subject is minha mãe, which is third-person singular.

In the present tense:

• eu gosto / adoro
• você gosta / adora
• ele/ela gosta / adora

Since minha mãe = ela, the correct forms are:

• gosta
• adora

Yes, both words contain nasal vowels, which can be tricky for English speakers.

• mãe has a nasal sound somewhat like maing, but without fully pronouncing a final ng
• não sounds roughly like nowng, again with nasalization instead of a clear final consonant

A few tips:

• Don’t try to pronounce them like plain English my or now
• Let some air resonate through your nose
• The final -m or -o spelling is not pronounced like a strong English consonant

These nasal sounds are very important in Brazilian Portuguese, so they are worth practicing early.

Because mas is connecting two complete clauses, and in Portuguese it is standard to place a comma before it in this kind of sentence:

• Minha mãe não gosta de pepino, mas adora salada de repolho.

This is very similar to English punctuation with but when it joins two full clauses.