Quando o tempo está bonito, eu gosto de caminhar no bairro.

Here o tempo means the weather.

In Portuguese, tempo can mean both time and weather, so context matters:

• Não tenho tempo. = I don’t have time.
• O tempo está bonito. = The weather is nice.

Using o helps make it sound natural here, because o tempo is a very common way to talk about weather.

Portuguese usually uses estar for temporary conditions or states, and weather conditions are treated that way.

So:

• O tempo está bonito. = The weather is nice.
• O tempo está ruim. = The weather is bad.

Using ser here would sound wrong or very unnatural. In this sentence, the weather is being described as it is at that moment / in that situation, so estar is the right verb.

Because bonito agrees with tempo, and tempo is a masculine noun.

• o tempo → masculine
• so the adjective is bonito

If the noun were feminine, the adjective would usually change:

• a cidade bonita = the beautiful city

But here it must be o tempo bonito or o tempo está bonito.

Yes, it is natural. It means the weather is nice, pleasant, or beautiful.

That said, Brazilians also very often say things like:

• O tempo está bom. = The weather is good.
• Está um dia bonito. = It’s a beautiful day.
• Está ensolarado. = It’s sunny.

So bonito is fine and natural, but it sounds a little more descriptive than the very common bom.

Yes, you can leave it out.

Portuguese often drops subject pronouns when the meaning is already clear from the verb:

• Eu gosto de caminhar no bairro.
• Gosto de caminhar no bairro.

Both are correct.

Including eu can add a little emphasis or clarity, but it is not required here.

Because the verb gostar normally requires the preposition de.

So you say:

• gosto de caminhar = I like walking / I like to walk
• gosto de café = I like coffee
• gosto de música = I like music

This is just part of how gostar works in Portuguese. English speakers often want to leave out de, but in standard Portuguese it should be there.

Both verbs are in the present indicative:

• está = present of estar
• gosto = present of gostar

In this sentence, the present tense expresses a general habit or usual preference:

• Quando o tempo está bonito, eu gosto de caminhar no bairro. = Whenever the weather is nice, I like to walk in the neighborhood.

So this is not necessarily about only one specific day. It sounds like a regular pattern.

Caminhar means to walk, often in a fairly straightforward sense.

You could use andar in some contexts, but the two are not always identical:

• caminhar = to walk
• andar = to walk, but also to go around, to move, or even to ride/travel in some contexts

For example:

• Gosto de caminhar no bairro. = I like walking in the neighborhood.
• Gosto de andar pelo bairro. = I like walking/going around the neighborhood.

Caminhar is a very good choice if you specifically mean walking.

Sometimes, yes, but the meaning changes a bit.

• caminhar focuses on the act of walking
• passear focuses more on going out for leisure, strolling, or spending time out

So:

• Gosto de caminhar no bairro. = I like to walk in the neighborhood.
• Gosto de passear pelo bairro. = I like to stroll around the neighborhood.

If you want the idea of a relaxing stroll, passear can work well. If you simply mean walking, caminhar is more direct.

No is a contraction of:

• em + o = no

So:

• no bairro = in the neighborhood

This is very common in Portuguese:

• na cidade = in the city
• no parque = in the park
• no bairro = in the neighborhood

In this sentence, no bairro suggests walking within the neighborhood area. If you want to emphasize around the neighborhood, pelo bairro is also very common.

In many situations, yes.

There is a small difference:

• no bairro = in the neighborhood
• pelo bairro = around the neighborhood / through the neighborhood

If you are imagining someone walking around the streets of the neighborhood, pelo bairro can sound especially natural.

So both can work, but they highlight slightly different things:

• caminhar no bairro = walk in the neighborhood
• caminhar pelo bairro = walk around the neighborhood

Because that first part is a dependent clause placed before the main clause.

Structure:

• Quando o tempo está bonito, = when the weather is nice
• eu gosto de caminhar no bairro. = I like to walk in the neighborhood

In Portuguese, it is normal to put a comma after an introductory clause like this.

If you reverse the order, the comma is often omitted:

• Eu gosto de caminhar no bairro quando o tempo está bonito.

Yes. This is completely natural:

• Eu gosto de caminhar no bairro quando o tempo está bonito.

That means the same thing as the original sentence. The difference is mostly about focus and style:

• Quando o tempo está bonito, eu gosto de caminhar no bairro.
  This emphasizes the weather condition first.
• Eu gosto de caminhar no bairro quando o tempo está bonito.
  This starts with your preference first.

Because quando is simply spelled that way in Portuguese. It does not take an accent.

This is true both when it means when in a statement and in a question:

• Quando o tempo está bonito... = When the weather is nice...
• Quando você chega? = When are you arriving?

So if you are coming from Spanish or expecting an accent for question words, Portuguese is different here: quando has no accent.

Usually it sounds like a general habit.

• Quando o tempo está bonito = whenever the weather is nice
• eu gosto de caminhar no bairro = I like to walk in the neighborhood

So the full sentence suggests something you generally enjoy doing under that condition.

If you wanted a more specific one-time meaning, you would usually need more context, or you might use a different tense or wording.