A faxina demorou porque havia muita bagunça debaixo da cama e atrás da porta.

Yes. Faxina usually means a more substantial cleaning, like a house-cleaning or a thorough cleanup. It often suggests more work than the more general word limpeza.

• faxina = cleanup / house-cleaning / deep cleaning
• limpeza = cleaning in a broader, more general sense

So A faxina demorou sounds like The cleaning took a long time or The cleanup took a while.

Portuguese uses definite articles more often than English. Here, a means the, and a faxina refers to a specific cleaning event the speaker has in mind.

So:

• A faxina demorou = The cleaning took a long time
• Faxina demorou would sound incomplete or unnatural in this context

Demorou is the preterite form of demorar. In this kind of sentence, demorar means to take time or to take a long time.

So:

• A faxina demorou = The cleaning took a while
• literally, something like The cleaning delayed/lasted, but in natural English it is better understood as took a long time

This is a very common structure in Portuguese:

• A reunião demorou. = The meeting took a long time.
• O almoço demorou. = Lunch took a while.

Because here it introduces a reason: because.

In Portuguese, these forms are different:

• porque = because
• por que = why / for what reason
• por quê = why, when it comes at the end
• porquê = the reason, as a noun

In this sentence, the idea is The cleaning took a long time because..., so porque is the correct form.

Here havia is the past form of haver used in an existential sense, meaning there was or there were.

So:

• havia muita bagunça = there was a lot of mess
• more literally, there existed a lot of mess

This use of haver is very common in writing and in standard Portuguese.

In Brazil, yes, many people say tinha muita bagunça in everyday speech, meaning there was a lot of mess. But there is an important difference in style:

• havia muita bagunça = more standard, more formal, very natural in writing
• tinha muita bagunça = very common in spoken Brazilian Portuguese, more informal

So the sentence with havia sounds a bit more careful or written.

Because existential haver is impersonal in standard Portuguese. That means it does not agree with what comes after it and stays in the singular.

So standard Portuguese says:

• havia muita bagunça
• havia muitos problemas
• havia várias pessoas

Not:

• haviam muitos problemas
• haviam várias pessoas

Even when the following noun is plural, haver stays singular in this existential use.

Because bagunça here is being used like an uncountable noun, similar to mess, clutter, or disorder in English.

So:

• muita bagunça = a lot of mess / a lot of clutter

Portuguese often uses bagunça in the singular when talking about mess in a general sense. You could use the plural in some contexts, but it would be less natural here.

Because muita agrees with bagunça, and bagunça is feminine singular.

Agreement in Portuguese is important:

• muita bagunça = feminine singular
• muito barulho = masculine singular
• muitas coisas = feminine plural
• muitos objetos = masculine plural

So muita is correct because bagunça is feminine.

Debaixo de is a prepositional expression meaning under or underneath.

So:

• debaixo da cama = under the bed

The full structure is:

• debaixo de + noun

But when de is followed by the feminine article a, it contracts:

• de + a = da

So debaixo da cama is really debaixo de a cama, but the contracted form da is the one actually used.

Atrás de is another prepositional expression, and it means behind.

So:

• atrás da porta = behind the door

Again, the structure is:

• atrás de + noun

And again:

• de + a = da

So atrás da porta is the natural contracted form.

Because both cama and porta are feminine nouns that normally take the article a.

The contraction works like this:

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

So:

• debaixo da cama
• atrás da porta

If the noun were masculine, you would usually see do instead:

• debaixo do sofá
• atrás do armário

Yes. In Brazilian Portuguese, debaixo de and embaixo de are often used with very similar meanings.

So both are natural:

• debaixo da cama
• embaixo da cama

In many situations, they are basically interchangeable. A learner can safely understand both as under the bed.

This is a very common past-tense contrast in Portuguese.

• demorou describes the main completed event: the cleaning took a long time
• havia gives background information: there was a lot of mess there during that situation

So the sentence separates:

1. the main event that happened and finished
2. the ongoing background condition that explains it

That is why this combination sounds natural:

• A faxina demorou = completed event
• porque havia muita bagunça... = background reason/state

Yes, to some extent. Portuguese is flexible enough that you could reorder the sentence and still keep the same meaning.

For example:

• Porque havia muita bagunça debaixo da cama e atrás da porta, a faxina demorou.
• Havia muita bagunça debaixo da cama e atrás da porta, por isso a faxina demorou.

The original version is very natural and straightforward, but these alternatives are also possible.