Janeiro é o mês em que minha família gosta de caminhar na praia.

Normally, months are written in lowercase in Portuguese: janeiro, fevereiro, etc.

In this sentence, Janeiro is capitalized because it is the first word of the sentence. If it appeared in the middle, you would usually write janeiro.

Janeiro is a proper name, so it usually appears without an article in this kind of sentence.

Mês is a common noun, and here it is being identified specifically: the month. That is why Portuguese uses o mês.

So:

• Janeiro = proper noun
• o mês = specific common noun

Em que means something like in which or when, depending on how natural you want the English to sound.

In o mês em que..., it connects mês to the rest of the sentence:

• o mês em que minha família gosta de caminhar na praia
• literally: the month in which my family likes to walk on the beach

It is a very common structure in Portuguese after words for time, place, and other nouns:

• a cidade em que moro = the city where I live
• o dia em que cheguei = the day when I arrived

Because família is grammatically singular in Portuguese.

Even though a family contains several people, the noun itself is singular, so the verb is also singular:

• minha família gosta

If the subject were plural, then the verb would be plural:

• meus parentes gostam
• meus familiares gostam

This works the same way as English my family likes in more formal singular agreement.

Because gostar normally requires the preposition de.

So in Portuguese, you say:

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

Examples:

• Eu gosto de música.
• Ela gosta de nadar.
• Minha família gosta de caminhar.

So gosta de caminhar is the correct pattern.

After gostar de, when you talk about liking an action in general, Portuguese uses the infinitive.

So:

• gosta de caminhar = likes to walk / likes walking

This is very common:

• gosto de ler
• gostam de viajar
• ela gosta de cozinhar

Portuguese does not usually use a form equivalent to English likes walking with a gerund here. The infinitive is the normal choice.

Both can relate to walking, but they are not always interchangeable.

Caminhar usually means to walk as an activity, often with the sense of walking for pleasure, exercise, or movement on foot.

Andar can also mean to walk, but it is broader and can mean to go around, to move, or even appear in many idiomatic uses.

In this sentence, caminhar na praia sounds very natural because it suggests the activity of walking along the beach.

Na is a contraction of em + a:

• em a praia becomes na praia

This is extremely common in Portuguese.

Other examples:

• no parque = em + o parque
• nos Estados Unidos = em + os
• nas férias = em + as

Here, na praia means on the beach or at the beach, depending on context.

Portuguese uses definite articles more often than English, especially with places and locations.

So expressions like these are very normal:

• na praia
• no parque
• na escola
• no cinema

Even when English may sound a bit less explicit, Portuguese often prefers the article as part of the standard expression.

Yes. A simpler and more direct version would be:

Minha família gosta de caminhar na praia em janeiro.

That version is perfectly natural. The original sentence: Janeiro é o mês em que minha família gosta de caminhar na praia puts extra focus on January by making it the topic of the sentence.

So the difference is mainly emphasis, not basic meaning.

A rough pronunciation guide is:

• janeiro ≈ zhah-NAY-roo
• minha ≈ MEEN-ya

A few details:

• The j in Brazilian Portuguese often sounds like the s in measure or the zh sound.
• The ei in janeiro sounds like ay.
• The nh in minha is a special Portuguese sound, similar to the ny in canyon.

So:

• janeiro = zhah-NAY-roo
• minha família ≈ MEEN-ya fah-MEE-lee-ah