Learn Hardcore Portuguese (Brazil): No domingo vamos fazer um churrasco no quintal com bolo de chocolate. - On Sunday we are going to have a barbecue in the backyard with chocolate cake.

No domingo vamos fazer… – very common, neutral speech.
Domingo vamos fazer… – also common, a bit shorter and slightly more informal.
Em domingo is not used for specific Sundays like this; it sounds wrong here.

So no domingo and domingo (without anything) are both fine, but no domingo is the most typical way to say “on Sunday” in this kind of sentence.

Why vamos fazer instead of the simple future faremos?

Vamos fazer is ir (present) + infinitive, a very common way to talk about the future in Brazilian Portuguese, especially for plans and intentions:

Vamos fazer um churrasco ≈ “We’re going to have a barbecue / We’re going to make a barbecue.”

The simple future faremos exists but is:

more formal or written, and
often used for promises, instructions, or more distant/less personal events.

Everyday Brazilian speech strongly prefers ir + infinitive, so vamos fazer sounds much more natural than faremos in this context.

Why fazer um churrasco and not ter um churrasco or just fazer churrasco?

In Brazilian Portuguese, the most idiomatic way to say “have a barbecue (host one)” is fazer um churrasco.

fazer um churrasco – to organize/host a barbecue event.
ter um churrasco – possible, but less common; can sound more like “there will be a barbecue” than “we’re the ones putting it on”.
fazer churrasco (without um) – more general or habitual: “to do barbecue / to barbecue”, not necessarily “a specific barbecue event”.

So vamos fazer um churrasco clearly means a specific barbecue we’re planning to have.

Why is there an article in um churrasco, but not in bolo de chocolate? Why not com um bolo de chocolate?

Both versions with the cake are actually possible:

com bolo de chocolate – literally “with chocolate cake”, talking about having chocolate cake as part of the menu, in a general way.
com um bolo de chocolate – “with a chocolate cake”, a specific one cake (for example, one big cake somebody will bring).

After com, Brazilians very often use a bare singular noun when they mean “there will be X as part of it”:

churrasco com salada, arroz e bolo de chocolate
“barbecue with salad, rice, and chocolate cake”

So in this sentence, com bolo de chocolate is the most natural way to say “with chocolate cake (as part of what we’ll eat).”

What exactly does churrasco mean here? Is it just the grilled meat?

In Brazilian Portuguese, churrasco usually means the whole barbecue event, not just the meat:

the gathering,
the grill,
the drinks,
side dishes,
desserts, etc.

So fazer um churrasco is “have/host a barbecue (party),” and the meat is just one part of it. That’s why it sounds natural to say um churrasco … com bolo de chocolate: you’re describing what will be served at that event.

What is quintal exactly? Is it “yard”, “garden”, or “backyard”?

Quintal in Brazilian Portuguese usually means a backyard or back area of a house:

Often not a decorative garden, but a practical outdoor space: where you might have a grill, clothesline, storage, plants, etc.
It’s typically behind or around the house.

If you want “garden” in the more decorative sense (flowers, lawn, front yard), Brazilians often say jardim.

So no quintal is best translated as “in the backyard” here.

Why no quintal and not em quintal or no jardim?

Just like with no domingo, no quintal is em + o quintal:

em o quintal → no quintal = “in the backyard”

You can’t say em quintal here because quintal usually needs an article (o quintal, “the backyard”). So it has to contract to no.

You could say no jardim if you really mean “in the (flower) garden / front yard,” but quintal and jardim aren’t interchangeable; they describe different kinds of outdoor spaces.

Does com bolo de chocolate mean we’re eating the barbecue together with the cake, like at the same time?

Not necessarily. Com here mainly means “including / accompanied by”:

um churrasco no quintal com bolo de chocolate
= “a backyard barbecue that includes chocolate cake (on the menu).”

It doesn’t say when the cake will be eaten. It just means that as part of this barbecue event, there will also be chocolate cake (probably as dessert).

Why bolo de chocolate and not bolo com chocolate? Is there a difference?

Yes, there’s a nuance:

bolo de chocolate – the cake’s main flavor/identity is chocolate (a “chocolate cake”).
bolo com chocolate – a cake that has chocolate with it in some way (as an ingredient, in the filling, on top, etc.), but the identity is less strongly “a chocolate cake.”

In practice, bolo de chocolate is the standard way to say “chocolate cake.” Bolo com chocolate sounds more like you’re emphasizing chocolate as one of several ingredients or toppings.

Are all the nouns here masculine? How can I tell?

Yes, all the key nouns in this sentence are masculine:

o domingo → no domingo
um churrasco
o quintal → no quintal
o bolo de chocolate

You can see it from:

the articles: o / um (masculine), not a / uma (feminine),
the typical -o ending in domingo, churrasco, quintal, bolo (very often masculine in Portuguese).

This is why we say no domingo, um churrasco, no quintal, (um) bolo and not na domingo, uma churrasco, na quintal, uma bolo, etc.