Não só a camisa, mas também a saia estão no cabide.

Because não só ... mas também ... is a fixed expression meaning not only ... but also ....

So não here does not make the whole sentence negative. It is just part of the pattern:

• não só X, mas também Y
• not only X, but also Y

It adds emphasis. The speaker is saying that one thing is true, and another thing is true as well.

A simple e just joins two items:

• A camisa e a saia estão no cabide.
• The shirt and the skirt are on the hanger.

But não só ..., mas também ... adds emphasis and contrast. It suggests something like:

• not just the shirt — the skirt too

It is often used when the speaker wants to expand or correct an expectation.

Because together they form a compound subject:

• a camisa
  • a saia

When two singular nouns are linked this way, the verb normally goes in the plural:

• A camisa e a saia estão ...
• Não só a camisa, mas também a saia estão ...

So estão is the standard agreement here.

In standard Portuguese, estão is the expected form.

You may occasionally hear singular agreement in informal speech, especially when the speaker mentally focuses on the nearest noun or on the idea as a whole, but for learners, the safe and correct choice here is:

• Não só a camisa, mas também a saia estão no cabide.

So in practice, use estão.

Portuguese uses definite articles more often than English does.

Here, each item is presented as a specific thing, so each noun keeps its article:

• a camisa
• a saia

This is very normal in Portuguese. English might say the shirt and the skirt, but Portuguese often repeats the article more consistently.

No is a contraction of:

• em + o = no

So:

• no cabide = on/in the hanger

Because cabide is masculine singular, you use o, which gives no.

Compare:

• na mesa = em + a
• nos armários = em + os
• nas caixas = em + as

Because cabide is a masculine noun:

• o cabide

So the contraction must be:

• em + o = no

If the noun were feminine, then you would use na:

• a cadeira → na cadeira

Yes. Cabide is the normal everyday word for a clothes hanger.

So estão no cabide means the clothes are on a hanger. Depending on context, a speaker might also say something more explicit like estão penduradas no cabide if they want to stress that the clothes are hanging, but no cabide by itself is perfectly natural.

The comma is very common and helps mark the two parts of the correlative structure:

• Não só a camisa, mas também a saia ...

It makes the sentence easier to read and sounds natural in writing. In less careful writing, people may omit it sometimes, but using the comma here is a good choice.

Yes. Portuguese has several very common alternatives, such as:

• não só ..., mas também ...
• não apenas ..., mas também ...
• não somente ..., mas também ...
• não só ..., como também ...

All of these mean roughly not only ..., but also .... Some sound a bit more formal than others, but they are all standard.

Not always. Camisa often means shirt, especially a button-up shirt or a more standard shirt.

But Brazilian Portuguese also uses:

• camiseta for T-shirt
• blusa for certain kinds of tops or blouses

So camisa is correct here, but the exact choice depends on the type of clothing.

Yes, though the emphasis may shift. For example:

• Não só a camisa, mas também a saia estão no cabide.
• No cabide estão não só a camisa, mas também a saia.

Both are grammatical. The original version is more straightforward. The second version highlights no cabide first, which can sound more literary or emphatic.

You would usually say:

• A camisa e a saia estão no cabide.

That is the plain, neutral version.
The original sentence is more emphatic because it uses não só ..., mas também ....