Learn Hardcore Russian: Вчера мы смотрели страшный фильм, и моя сестра закрывала глаза. - Yesterday we watched a scary movie, and my sister was closing her eyes.

In this sentence смотрели presents the watching as a process or background action: “we were watching / we watched (as an ongoing activity)”. It doesn’t stress completion.

If you say Вчера мы посмотрели страшный фильм, you emphasize the result: you finished watching the film. The original sentence focuses more on what was going on when the sister was closing her eyes, so the imperfective смотрели fits better.

Why is закрывала used and not закрыла?

Again, this is aspect:

закрывала – past, imperfective (закрывать)
закрыла – past, perfective (закрыть)

Закрывала глаза suggests an ongoing or repeated action during the film:
“She kept closing her eyes / was closing her eyes (whenever it was scary).”

If you say моя сестра закрыла глаза, it sounds like she closed her eyes once at a particular moment and that’s it. Here, the idea is that she repeatedly or continually did it, so the imperfective закрывала is used.

Why is it страшный фильм and not some other form like страшного фильма?

The verb смотреть takes its object in the accusative case:

Nom.: страшный фильм
Acc.: страшный фильм (same form for inanimate masculine nouns)

So страшный фильм here is accusative, even though it looks like nominative.

Страшного фильма is genitive; that would be used in other contexts (e.g. бояться страшного фильма – “to be afraid of the scary film”), but смотреть needs the accusative: смотреть страшный фильм.

Why is страшный in the form страшный, not страшное or страшная?

Adjectives must agree with the noun in gender, number, and case.

фильм is masculine, singular, accusative (same form as nominative).
So the adjective must also be masculine singular accusative → страшный.

Other forms would match different nouns:

страшная → feminine (e.g. страшная книга)
страшное → neuter (e.g. страшное кино in some contexts)
страшные → plural (e.g. страшные фильмы)

Why is фильм not visibly in the accusative case?

For inanimate masculine nouns, nominative and accusative forms are identical in the singular:

Nom.: фильм
Acc.: фильм

You know it’s accusative only because of the verb: смотреть что? → смотреть фильм.

With animate masculine nouns, accusative equals genitive (e.g. вижу друга, not вижу друг), but with inanimate nouns like фильм, nominative and accusative look the same.

Why do we say глаза and not глаз or something like глазами?

Глаза is the nominative/accusative plural of глаз (“eye”):

one eye – глаз
two eyes – глаза

The verb закрывать takes its object in the accusative: закрывать что? → глаза.

Other forms:

глазами – instrumental plural (“with (her) eyes”)
глаз – genitive plural (“of (her) eyes”), used in other structures, not after закрывать.

Why is it моя сестра and not мою сестру?

Here моя сестра is the subject of the second clause, so it must be in the nominative case:

Nom. subject: моя сестра закрывала глаза – “my sister closed/was closing her eyes.”
Accusative (мою сестру) would be an object, not a subject: e.g. я вижу мою сестру – “I see my sister.”

So nominative: моя сестра is required.

Why is the past tense смотрели but закрывала? Why are the endings different?

The Russian past tense agrees with the subject in gender and number:

мы смотрели – мы is plural → past plural ending -ли → смотрели
моя сестра закрывала – сестра is feminine singular → past feminine ending -ла → закрывала

Other forms of these verbs in the past:

смотреть: смотрел (masc.), смотрела (fem.), смотрело (neut.), смотрели (pl.)
закрывать: закрывал, закрывала, закрывало, закрывали

Why is Вчера at the beginning? Could I say Мы вчера смотрели… or Мы смотрели страшный фильм вчера?

All of these are grammatically correct:

Вчера мы смотрели страшный фильм…
Мы вчера смотрели страшный фильм…
Мы смотрели вчера страшный фильм…

Russian word order is fairly flexible. Putting Вчера at the beginning makes the time frame the starting point of the sentence (what happened yesterday? → we watched a scary film).

Moving вчера later usually doesn’t change the basic meaning, but can slightly shift emphasis in context (e.g. emphasizing we rather than yesterday). For a neutral statement, all three variants are acceptable.

Why is there a comma before и?

Russian usually puts a comma before и when it joins two independent clauses (each with its own subject and verb):

Clause 1: мы смотрели страшный фильм (subject мы, verb смотрели)
Clause 2: моя сестра закрывала глаза (subject моя сестра, verb закрывала)

So this is a compound sentence, and the comma is required:
…фильм, и моя сестра…

If the clauses had the same subject and were very close, sometimes the comma can be omitted, but with different subjects like мы and моя сестра, the comma is standard.

Why isn’t it закрывала свои глаза (“her eyes”)? How do we know whose eyes they are?

In Russian, if it’s obvious that something belongs to the subject, you often omit a possessive:

моя сестра закрывала глаза is naturally understood as “my sister closed her eyes.”

You can say закрывала свои глаза, but:

It sounds more emphatic or stylistically heavier, and
свои is usually used when you need to contrast with someone else’s things (e.g. “she closed her own eyes, not someone else’s”).

So the shorter закрывала глаза is the most natural here.

Could we say мы смотрели страшное кино instead of страшный фильм?

Yes, but there is a nuance:

фильм – a specific film/movie as an object (more concrete)
кино – can mean “cinema” in general or “movies” as a medium; страшное кино can sound a bit more colloquial or genre-like.

Вчера мы смотрели страшный фильм – focuses on a particular movie.
Вчера мы смотрели страшное кино – sounds more like “we watched some scary movie / a horror movie,” a bit more general.

Both are understandable; фильм is often safer for a specific movie.

Why doesn’t Russian use a word for “the” in страшный фильм?

Russian has no articles (“a”, “an”, “the”). Definiteness/indefiniteness is inferred from context, word order, and sometimes stress.

So страшный фильм can mean:

“a scary film”
or “the scary film”

Depending on what has already been mentioned or is known to the speakers. In this sentence, context (e.g. the rest of the conversation) would tell you whether it’s “a” or “the” in English, but in Russian the phrase itself stays the same.