A vitrine daquela loja no shopping está bonita, mas eu quero ver o provador antes de comprar.

Portuguese uses articles much more often than English. Here, a vitrine means the display window / the shop window. In English, we might sometimes drop the, but in Portuguese it is very normal to include it.

So:

• a vitrine = the window display
• uma vitrine = a window display

In this sentence, the speaker is talking about a specific one, so a is the natural choice.

Vitrine usually means a store window, shop window, or window display—the area where products are shown to attract customers.

In Brazilian Portuguese, it can refer both to:

• the physical front display window
• the arrangement of products shown there

A learner might also see that in European Portuguese, montra is more common for this idea.

Daquela is a contraction of de + aquela.

So:

• aquela loja = that store
• daquela loja = of that store / from that store

In the sentence, A vitrine daquela loja means the window display of that store.

This kind of contraction is extremely common in Portuguese:

• de + o = do
• de + a = da
• de + aquele = daquele
• de + aquela = daquela

Portuguese has a three-way demonstrative system that is more detailed than English:

• esta = this, near the speaker
• essa = that, near the listener or already mentioned
• aquela = that, farther away from both

In real Brazilian Portuguese, people often use esse/essa more broadly than strict grammar rules suggest. But aquela loja gives the feeling of that store over there or that particular store at some distance.

So daquela loja sounds very natural if the speaker is pointing out or referring to a more distant store.

Yes. In Brazil, shopping is a very common short form for shopping center, meaning mall.

So:

• o shopping = the mall
• no shopping = in the mall or at the mall

No is the contraction of em + o:

• em o → no

This is one of the most important contractions in Portuguese:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

So loja no shopping means store in the mall.

Most naturally, it describes loja.

So the structure is:

• a vitrine [daquela loja no shopping]

That means:

• the display window [of that store in the mall]

In other words, it is the store that is in the mall. Because of the word order and normal interpretation, that is how most speakers would understand it.

This is the classic ser vs. estar question.

Here, está bonita suggests a current appearance or condition:

• The display looks nice
• The display is looking pretty right now

That makes sense because a store window display can change often.

If you said é bonita, it would sound more like a general or permanent quality:

• The display window is beautiful in general

So está bonita is the better choice when talking about how it looks at the moment.

Because bonita agrees with vitrine, and vitrine is a feminine singular noun.

Agreement in Portuguese is very important:

• a vitrine bonita
• o provador bonito

So:

• feminine singular noun → bonita
• masculine singular noun → bonito

Even though the store itself is loja, the adjective here is describing vitrine, not loja.

Yes, mas quero ver o provador... would also be grammatically correct.

Portuguese often drops subject pronouns because the verb form already shows the subject:

• quero already means I want

But eu is often included for:

• emphasis
• contrast
• clarity

After mas, adding eu can sound especially natural because it creates contrast:

• The display looks nice, but I want...

So mas eu quero feels a bit more explicit and contrastive than just mas quero.

Provador means fitting room or changing room in a store.

It comes from the verb provar, which in clothing contexts means:

• to try on

So:

• provar uma roupa = to try on a piece of clothing
• o provador = the fitting room

It is a masculine noun, so:

• o provador
• um provador

It is understandable, but it may sound a little unusual depending on the exact context.

Literally, ver o provador means see/check the fitting room. That can make sense if the speaker wants to:

• locate it
• inspect it
• make sure there is one
• see what it is like before buying

But in many shopping situations, a Brazilian speaker might more naturally say:

• quero experimentar antes de comprar = I want to try it on before buying
• quero ver se tem provador = I want to see if there’s a fitting room
• quero ir ao provador antes de comprar = I want to go to the fitting room before buying

So the original sentence is understandable, but there are slightly more idiomatic alternatives depending on the intended meaning.

After antes de, Portuguese very often uses the infinitive when the subject is the same as the subject of the main clause.

So:

• eu quero ver o provador antes de comprar means
• I want to see the fitting room before buying

The subject of comprar is understood to be the same I from eu quero.

You can say antes de eu comprar, but that usually sounds more explicit and is used when you really want to mention the subject:

• antes de eu comprar qualquer coisa = before I buy anything

In this sentence, the shorter antes de comprar is the most natural choice.

Portuguese often leaves out an object when it is obvious from context.

Here, comprar means something like:

• buy it
• buy the item
• buy the clothes
• make the purchase

The exact object is not stated because the listener can infer it. English does this too:

• I want to try it on before buying.

So the omission is completely normal.

Because mas is a coordinating conjunction meaning but, and in Portuguese it is standard to place a comma before it when it joins two clauses.

So:

• A vitrine... está bonita, mas eu quero...

This is the normal written pattern, just like in English:

• The display looks nice, but I want...

Yes, it is normal and natural.

The basic structure is:

• A vitrine = subject
• daquela loja no shopping = phrase describing which display window
• está bonita = verb + description

Portuguese often builds noun phrases this way:

• noun + identifying phrase

So the sentence flows naturally as:

• The display window of that store in the mall looks nice...

Nothing in the word order is strange for Brazilian Portuguese.