Quando o shopping fica lotado, eu saio da praça de alimentação e espero o trem do lado de fora.

In Brazilian Portuguese, shopping commonly means shopping mall. It is a shortened form of shopping center. So o shopping does not usually mean the activity of shopping here; it means the place.

It is treated as a masculine noun, so you get forms like:

• o shopping
• no shopping
• do shopping

This usage is very common in Brazil.

Ficar often means to become, to get, or to end up being. So o shopping fica lotado suggests the mall gets crowded.

By contrast, está lotado simply describes its state: it is crowded.

So the difference is roughly:

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

In a sentence about a repeated situation, fica lotado sounds very natural.

Because this sentence describes a habitual or repeated situation: Whenever the mall gets crowded, I leave...

In Portuguese, for repeated/general situations, quando is often followed by the present tense:

• Quando o shopping fica lotado...

If you were talking about one specific future event, Portuguese would normally use the future subjunctive:

• Quando o shopping ficar lotado...

So:

• quando fica = whenever it gets crowded / when it gets crowded generally
• quando ficar = when it gets crowded in the future

Lotado means packed, full, or crowded, often with the idea that a place is very full of people.

It is similar to cheio, but lotado is usually stronger and is especially common for places like:

• malls
• buses
• trains
• restaurants
• waiting rooms

So:

• cheio = full
• lotado = packed / crowded / jammed

In this sentence, lotado works very well because a mall can get very crowded.

Yes, it could just be saio.

Portuguese often drops subject pronouns because the verb ending already shows who the subject is:

• saio = I leave

So both are possible:

• eu saio
• saio

Including eu can add:

• a little emphasis
• clarity
• a more explicit style

In this sentence, eu is not required, but it is completely natural.

Because sair is conjugated irregularly in the first person singular.

The present tense is:

• eu saio
• você/ele/ela sai
• nós saímos
• vocês/eles/elas saem

So the correct form is saio.

This is a common verb pattern to memorize rather than build by rule from the infinitive.

Da is a contraction of:

• de + a = da

Here, sair usually takes de to show where someone is leaving from:

• sair de casa = to leave home
• sair do carro = to get out of the car
• sair da praça de alimentação = to leave the food court

So da praça de alimentação means from the food court.

No. Praça de alimentação is the normal Brazilian Portuguese term for a food court in a mall.

Literally, it looks something like food area or eating area, but the natural English equivalent is food court.

So even though praça often means square or plaza, in this expression the whole phrase should be understood as one unit:

• praça de alimentação = food court

Because esperar can take a direct object in Portuguese:

• esperar o trem
• esperar o ônibus
• esperar um amigo

This is extremely common and natural.

You can also hear esperar por:

• esperar pelo trem

Both are possible, but esperar o trem is very common and straightforward in Brazilian Portuguese.

So unlike English, Portuguese does not need a preposition there.

Do lado de fora is a common expression meaning outside or on the outside.

It breaks down like this:

• do = de + o
• lado = side
• de fora = of outside / outside

Literally it feels like on the outside side, but the natural meaning is simply:

• outside
• outside the building/place

So:

• espero o trem do lado de fora = I wait for the train outside

You could sometimes just say fora, but do lado de fora sounds a bit more specific and natural in many contexts.

Yes, it is the normal punctuation.

Quando o shopping fica lotado is an introductory subordinate clause. In Portuguese, when that kind of clause comes first, it is normally followed by a comma:

• Quando o shopping fica lotado, eu saio...

This is the same basic idea as in English:

• When the mall gets crowded, I leave...

So the comma is standard and recommended.

Yes, in this sentence trem clearly means train.

In some regional Brazilian speech, especially in Minas Gerais, trem can also be an informal word meaning something like thing/stuff. But that is not what is happening here.

Because the sentence says espero o trem and talks about waiting outside, the meaning is clearly the train.