De manhã, eu gosto de descascar uma banana e uma maçã para o café da manhã.

Because gostar normally requires the preposition de in Portuguese.

• gostar de + noun = to like something
  
  • Eu gosto de café.
• gostar de + infinitive = to like doing something
  
  • Eu gosto de correr.

So eu gosto de descascar... literally follows the normal Portuguese pattern for to like doing....

After gostar de, Portuguese uses the infinitive to talk about an action you like doing.

So:

• Eu gosto de descascar frutas. = I like peeling fruit.
• Ela gosta de estudar. = She likes studying.

English often uses -ing after like, but Portuguese usually uses the infinitive: gostar de + infinitive.

Not always. Portuguese often drops subject pronouns when the verb form already makes the subject clear.

So both are possible:

• Eu gosto de descascar uma banana...
• Gosto de descascar uma banana...

Both are natural. Including eu can add clarity, emphasis, or simply sound a little more explicit.

De manhã means in the morning. In Brazilian Portuguese, it is very common and natural.

Pela manhã also means in the morning, and it is usually a bit more formal or slightly more written-sounding.

Examples:

• De manhã, eu estudo.
• Pela manhã, eu estudo.

Both are correct. In everyday Brazilian speech, de manhã is extremely common.

Because De manhã is an introductory time expression placed at the beginning of the sentence.

Portuguese often uses a comma after this kind of opening phrase:

• De manhã, eu trabalho.
• À noite, ela lê.
• No domingo, nós descansamos.

The comma is not absolutely mandatory in every short sentence, but it is very common and helps readability.

It does repeat the morning idea a little, but not incorrectly.

• De manhã tells you when the person likes to do it.
• para o café da manhã tells you for what purpose/meal.

So the sentence is saying something like: in the morning, I like to peel a banana and an apple for breakfast.

It is grammatically fine, though a learner may notice that it feels a bit repetitive because breakfast already strongly suggests morning.

Yes, literally it comes from coffee of the morning, but as a whole expression it means breakfast.

This is a fixed expression in Portuguese:

• café da manhã = breakfast
• almoço = lunch
• jantar = dinner

Even if someone does not drink coffee, café da manhã still means breakfast.

Both can work, but they mean slightly different things.

• para o café da manhã = for breakfast
• no café da manhã = at breakfast / during breakfast

In your sentence, para o café da manhã suggests purpose: the fruit is being peeled to be eaten as breakfast.

Examples:

• Vou fazer ovos para o café da manhã. = I’m going to make eggs for breakfast.
• No café da manhã, eu como fruta. = At breakfast, I eat fruit.

Because each noun has its own article.

• uma banana e uma maçã = one banana and one apple

Repeating the article is normal and natural in Portuguese. It clearly marks two separate items.

If you said uma banana e maçã, it would sound incomplete or unnatural in this context.

Yes, but the meaning would become more general.

• descascar uma banana e uma maçã = peel a banana and an apple; it sounds like one specific banana and one specific apple
• descascar banana e maçã = peel banana and apple in a more general sense; this is less specific and may sound more informal or more like talking about types of food

In your sentence, using uma with both nouns is the most straightforward and natural choice.

Yes. Descascar means to peel and can be used with both.

Examples:

• descascar uma banana
• descascar uma maçã
• descascar batatas

For an apple, peeling is something you may or may not do, but the verb itself is perfectly natural.

Those marks show pronunciation.

• ç makes the s sound before a, o, or u
  So maçã sounds like ma-sã, not makã.
• ã shows a nasal vowel, which is very common in Portuguese.

So maçã is pronounced roughly like mah-SAHN with a nasal sound at the end, though there is no perfect English equivalent.

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

So you may hear:

• para o café da manhã
• pro café da manhã

Both are common in Brazil.
Para o is more neutral/full, while pro is very common in everyday speech.

Yes. Since café da manhã already implies morning, many speakers might prefer a simpler version, such as:

• Eu gosto de descascar uma banana e uma maçã para o café da manhã.
• De manhã, eu gosto de descascar uma banana e uma maçã.

Your original sentence is correct, but these versions may sound a little less repetitive depending on context.