Eu gosto de fritar alho no óleo antes de cozinhar o arroz.

Because gostar normally takes the preposition de in Portuguese.

So:

• gostar de algo = to like something
• gostar de fazer algo = to like doing something

That is why you say:

• Eu gosto de fritar alho not
• Eu gosto fritar alho

This is one of those verb-preposition combinations you just have to learn as a unit: gostar de.

Not always. In Brazilian Portuguese, subject pronouns are often included, but they can also be omitted when the meaning is clear.

So both are possible:

• Eu gosto de fritar alho no óleo antes de cozinhar o arroz.
• Gosto de fritar alho no óleo antes de cozinhar o arroz.

Because gosto is clearly I like, the sentence still makes sense without eu.

In Brazil, using eu is very common and natural, especially in speech, so the full sentence does not sound strange at all.

They are in the infinitive because they come after expressions that naturally lead into another verb.

Here:

• gosto de + infinitive → gosto de fritar
• antes de + infinitive → antes de cozinhar

English often uses -ing in similar places:

• I like frying...
• before cooking...

Portuguese usually uses the infinitive instead:

• gosto de fritar...
• antes de cozinhar...

So this is a very normal Portuguese structure.

Fritar means to fry.

Cozinhar means to cook in a general sense.

So in this sentence:

• fritar alho no óleo = to fry garlic in oil
• cozinhar o arroz = to cook the rice

Even though rice is often boiled, Portuguese still commonly uses cozinhar as the general verb. You do not need a special verb here.

No is a contraction of em + o.

So:

• em o óleo → no óleo

It means in the oil.

This kind of contraction is very common in Portuguese:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

So fritar alho no óleo literally means to fry garlic in the oil.

Portuguese uses articles differently from English, especially with food and ingredients.

In this sentence:

• alho is being treated as an ingredient in a general way, so no article is fine.
• o arroz often refers to the rice being cooked for the meal, so the article sounds very natural.

So cozinhar o arroz is a common way to say cook the rice.

Could you hear cozinhar arroz too? Yes, sometimes. But cozinhar o arroz often sounds more specific and natural in this kind of everyday cooking context.

Because antes de is used before an infinitive.

So:

• antes de cozinhar o arroz = before cooking the rice

You use antes que when a full clause follows, usually with a different subject, and the verb after it goes in the subjunctive.

For example:

• Vou fritar o alho antes de cozinhar o arroz.
• Vou fritar o alho antes que o arroz esfrie.

So in your sentence, since the structure is before + verb, antes de + infinitive is the correct pattern.

Alho can be tricky because of lh.

A rough English-friendly approximation is:

• A-lyo

More exactly, in Brazilian Portuguese it is roughly:

• /ˈa.ʎu/

The lh sound is similar to the lli in some pronunciations of million, though it is not exactly the same.

So:

• alho ≈ AH-lyoo

It is not pronounced like English al-ho.

In Brazilian Portuguese, arroz is roughly:

• ah-HOHS or
• ah-HOZ depending on accent and pronunciation style

A few pronunciation points:

• the initial rr in Brazilian Portuguese often sounds like an English h or a throaty r
• the stress is on the second syllable
• the final z may sound like s or z depending on region and phonetic context

A useful approximation is:

• ah-HOHS

Not necessarily. Óleo usually means oil in a general sense, especially cooking oil.

If you specifically mean olive oil, the usual word is:

• azeite

So:

• óleo = cooking oil / oil in general
• azeite = olive oil

That means this sentence most naturally suggests regular cooking oil, unless the context says otherwise.

It describes a general preference or usual practice, not something happening right now.

Eu gosto de... means I like to... or I enjoy...

So the sentence means something like:

• this is how I like to do it
• this is my preferred method
• this is a usual habit in cooking

If you wanted to talk about what you are doing right now, you would normally use a different structure, such as:

• Estou fritando alho no óleo antes de cozinhar o arroz.

It is understandable and grammatically correct. However, in cooking, many Brazilians would often say refogar alho no óleo if they mean to sauté garlic lightly in oil rather than fully fry it.

So these can feel slightly different:

• fritar alho = fry garlic
• refogar alho = sauté garlic / cook garlic briefly in oil

If the idea is the common Brazilian step of lightly cooking garlic in oil before making rice, refogar may sound especially natural. But your sentence with fritar is still understandable and acceptable.