Em fevereiro, a cidade fica cheia por causa do Carnaval, mas eu gosto do ambiente.

With months in Portuguese, the usual preposition for in is em:

• em fevereiro = in February
• em março = in March

You normally do not use the article here, so no fevereiro is not the standard form.

A few examples:

• Em janeiro, faz frio.
• Em agosto, vou de férias.

Here, fica means something like becomes, gets, or ends up being.

So:

• a cidade fica cheia = the city gets crowded / becomes full

The verb ficar is very common in Portuguese and often describes a change of state:

• ficar cansado = to get tired
• ficar triste = to become sad
• ficar cheio = to become full / crowded

In this sentence, it does not mean stay in the literal location sense.

Because cheia agrees with a cidade, which is a feminine singular noun.

Agreement in Portuguese:

• masculine singular: cheio
• feminine singular: cheia
• masculine plural: cheios
• feminine plural: cheias

So:

• o bar fica cheio
• a cidade fica cheia
• as ruas ficam cheias

Yes, literally cheia means full, but in this context it is often best understood as:

• crowded
• packed
• very busy

So a cidade fica cheia is a natural way to say that the city becomes crowded during Carnival.

Por causa de means because of.

When de comes before the masculine singular article o, they contract:

• de + o = do

So:

• por causa de o Carnaval → por causa do Carnaval

Other common contractions:

• de + a = da
• de + os = dos
• de + as = das

Examples:

• por causa da chuva = because of the rain
• por causa dos turistas = because of the tourists

In Portuguese, Carnaval is usually capitalized when referring to the festival, just like a named celebration or holiday.

So:

• o Carnaval
• no Carnaval
• por causa do Carnaval

This is normal and standard.

Yes, it could be omitted.

Portuguese often leaves out subject pronouns because the verb ending already shows the person:

• gosto already means I like

So both are possible:

• mas eu gosto do ambiente
• mas gosto do ambiente

Including eu adds a bit of emphasis or contrast. Here it can sound like:

• but I like the atmosphere
• but as for me, I like the atmosphere

That fits well after the first clause about the city being crowded.

Because the verb gostar normally takes the preposition de.

So you say:

• gostar de algo = to like something

Examples:

• gosto de música
• gosto do verão
• gosto da cidade

In the sentence:

• de + o = do
• gosto do ambiente = I like the atmosphere

This is one of the most important patterns to remember with gostar.

Here, ambiente means atmosphere, vibe, or overall feel of the place.

So gosto do ambiente does not usually mean the natural environment here. In this sentence, it means something like:

• I like the atmosphere
• I like the vibe
• I like the mood

Because the context is Carnival, ambiente suggests the festive social atmosphere.

Mas means but.

It introduces a contrast:

• the city gets crowded because of Carnival
• but I like the atmosphere

So the speaker is saying that although the city is very full or crowded, they still enjoy it.

Do not confuse mas with mais:

• mas = but
• mais = more

Portuguese often puts a time expression at the beginning of the sentence, just like English:

• In February, the city gets crowded...

This structure is very natural:

• Em fevereiro, ...
• No verão, ...
• Durante o inverno, ...

You could also say:

• A cidade fica cheia em fevereiro...

Both are correct, but starting with Em fevereiro helps set the time frame immediately.

Sometimes yes, but the meaning changes slightly.

• fica cheia = gets crowded / becomes crowded
• está cheia = is crowded

In your sentence, fica cheia suggests what happens during that period every year: the city becomes crowded in February because of Carnival.

If you say está cheia, it sounds more like you are describing its condition right now.

In European Portuguese, some unstressed vowels are reduced a lot, so the sentence may sound more compressed than the spelling suggests.

A rough guide:

• Em fevereiro → something like uhm fuh-vuh-REI-roo
• a cidade → uh si-DA-d(uh)
• fica cheia → FEE-kuh SHAY-uh
• por causa do Carnaval → pur KAU-zuh du kar-nuh-VAL
• mas eu gosto do ambiente → maz eu GOSH-tu du ahm-bee-EN-t(uh)

A few useful pronunciation notes for European Portuguese:

• unstressed e often sounds like a very reduced vowel
• s at the end of mas sounds like z before eu
• de and do are often pronounced very lightly
• gosto in Portugal sounds like GOSH-tu

This is only an approximation, but it helps explain why spoken European Portuguese can sound much less transparent than the written form.