Вчера мы ходили не в кино, а в оперу, и в фойе было очень тихо.

Ходили is the past tense of ходить, a verb of motion that often implies a completed trip there and back, or going somewhere as an activity.

So Вчера мы ходили в оперу usually means something like Yesterday we went to the opera with the idea that it was an outing.

Compare:

• мы шли в оперу = we were walking/on the way to the opera
• мы пошли в оперу = we set off / went to the opera
• мы ходили в оперу = we went to the opera as a finished visit

In this sentence, ходили is the most natural choice for talking about yesterday’s outing.

This is a very common Russian contrast pattern:

• не X, а Y = not X, but Y

So:

• не в кино, а в оперу = not to the cinema, but to the opera

Russian uses а here, not но, because the speaker is correcting or replacing one idea with another.

Compare:

• не чай, а кофе = not tea, but coffee
• не сегодня, а завтра = not today, but tomorrow

Because after в with motion toward a place, Russian normally uses the accusative case.

• опера is a regular noun, so its accusative singular is оперу
• кино is an indeclinable noun, so it stays кино

So:

• в оперу = into/to the opera
• в кино = to the cinema

The difference is not because the grammar is different; it is because the nouns behave differently.

Кино is an indeclinable noun in modern Russian. That means it does not change form for case.

So you get:

• в кино
• из кино
• о кино

The same form is used each time.

This is common with some borrowed or shortened words in Russian.

Фойе is also an indeclinable noun, so it keeps the same form in all cases.

Here в фойе means in the foyer, so the meaning is location, not motion. Normally location after в takes the prepositional case, but since фойе is indeclinable, its form still stays фойе.

So:

• в фойе = in the foyer
• из фойе = from the foyer

Same form, different function.

Because Russian is using an impersonal construction here:

• в фойе было очень тихо = it was very quiet in the foyer

The word тихо is not a regular adjective here. It is a predicative word meaning quiet in the sense of the general atmosphere or condition.

In these impersonal past-tense sentences, Russian usually uses было, the neuter singular past form of быть, as a kind of default form.

So this structure means:

• It was quiet
• There was silence / it was very quiet

not

• the foyer was a quiet one

Here тихо functions as a predicative adverb or category-of-state word. In learner-friendly terms, it describes the overall situation, not a noun.

Compare:

• тихий зал = a quiet hall
  Here тихий is an adjective describing зал
• в зале тихо = it is quiet in the hall
  Here тихо describes the atmosphere

So in your sentence, тихо means quiet as a condition in the foyer.

The comma before а is required because а links two contrasting parts in the pattern не ..., а ....

So:

• не в кино, а в оперу

The comma before и is there because и joins another clause:

• Вчера мы ходили не в кино, а в оперу
• и в фойе было очень тихо

These are two separate predicative parts, so a comma is natural and standard.

No. Russian word order is flexible, and вчера could be moved for emphasis.

For example:

• Вчера мы ходили не в кино, а в оперу.
• Мы вчера ходили не в кино, а в оперу.

Both are correct. Putting вчера first is very natural because it sets the time right away.

Usually, in this sentence, the best translation is went:

• Вчера мы ходили... = Yesterday we went...

But in some contexts, ходили can be close to have been or used to go, depending on time words and context.

For example:

• Мы уже ходили в эту оперу = We’ve already been to this opera
• В детстве мы часто ходили в кино = As children, we often went to the cinema

So ходили is broader than simple English went, but here went is the most natural translation.