Ты не можешь не заметить, как в этой постановке меняются декорации.

In Russian, this structure does not simply cancel out the way it often does in English.
Не мочь не + infinitive means to be unable not to do something, or more naturally, you can’t help but notice.

So:

• Ты можешь заметить = You can notice
• Ты не можешь заметить = You cannot notice
• Ты не можешь не заметить = You cannot fail to notice / You can’t help noticing

It is a very common Russian pattern.

Заметить is the perfective verb, and here it fits because the idea is to notice something as a single result or completed perception.

Compare:

• заметить = to notice
• замечать = to notice habitually / to be noticing / to keep noticing

In не можешь не заметить, Russian uses the perfective because the meaning is basically you can’t fail to notice it—that is, the noticing happens as a result.

Yes, ты could be omitted, because Russian often leaves out subject pronouns when they are clear from the verb form.

• Не можешь не заметить... would still clearly mean You can’t help noticing...

Including ты can make the sentence:

• more direct,
• more conversational,
• or slightly more emphatic.

Also, ты is the informal singular you. If you wanted the formal or plural version, it would be:

• Вы не можете не заметить...

Here как introduces a subordinate clause meaning something like how.

So:

• Ты не можешь не заметить, как... = You can’t help noticing how... or = You can’t fail to notice that/how...

In this sentence, как в этой постановке меняются декорации describes what you notice.

It is not asking a question. It is functioning as a connector inside the sentence.

В этой постановке is in the prepositional case because it follows в in the meaning in.

Forms here:

• эта постановка = this production/staging
• в этой постановке = in this production

The prepositional endings are:

• этой for the feminine adjective/pronoun
• постановке for the feminine noun

So the phrase literally means in this production or in this staging.

Постановка can mean staging, production, or performance setup, especially in theater.

In this sentence, it most naturally refers to a theatrical production or the way a play is staged.

So в этой постановке is something like:

• in this production
• in this staging

The best translation depends on context, but the Russian word strongly suggests a theatrical setting.

Декорации is very often used in the plural in Russian when talking about stage scenery / sets.

So:

• декорация = one decoration / one set element
• декорации = scenery, stage sets, set pieces

Even when English might use a collective word like the scenery or the set, Russian commonly uses the plural декорации.

Меняются is the 3rd person plural present tense of меняться.

Breakdown:

• меняться = to change
• они меняются = they change / are changing

Here the subject is декорации, which is plural, so the verb must also be plural:

• декорации меняются = the sets change / the scenery changes

The ending -ются shows:

• present tense,
• plural,
• reflexive verb.

Менять is usually transitive: to change something.

• Они меняют декорации = They are changing the sets

Меняться is intransitive/reflexive: to change, to be changing.

• Декорации меняются = The sets are changing / The scenery changes

So in your sentence, the sets themselves are the grammatical subject, which is why меняются is used.

It can mean either, depending on context.

Russian present tense often covers both:

• they change
• they are changing

In this sentence, English could naturally say:

• how the sets change in this production
• how the scenery changes in this production
• how the sets are changing in this production

If the sentence is describing what a viewer notices while watching, are changing may sound more vivid. If it describes a characteristic of the production, change may sound better.

Russian word order is flexible, and different orders can shift emphasis.

In как в этой постановке меняются декорации, putting в этой постановке earlier highlights the setting or context first:

• how, in this production, the sets change

If you said:

• как декорации меняются в этой постановке

that would still be grammatical, but it may sound slightly different in focus, with декорации introduced earlier.

The original order feels natural and stylistically smooth, especially if the speaker wants to emphasize this particular production.

Yes. Here как introduces a subordinate clause, so a comma is normally required:

• Ты не можешь не заметить, как...

Russian punctuation regularly uses commas before subordinate clauses more consistently than English does.

It is fairly neutral and natural, but не можешь не заметить has a slightly polished or rhetorical feel. It is common in both spoken and written Russian.

The sentence does not sound extremely formal, but it is a bit more elegant than a very simple everyday version.

For example, a more plain version might be:

• Ты обязательно заметишь, как в этой постановке меняются декорации. = You’ll definitely notice how the sets change in this production.

The original version is especially good for expressing it’s impossible not to notice this.