Learn Hardcore Russian: Сегодня вечером мы собираемся смотреть интересный фильм дома. - This evening we are going to watch an interesting movie at home.

If you only say сегодня, it could mean any time today. Сегодня вечером is more specific, just like in English “tonight / this evening” vs “today”.

What case is вечером in, and why is there no preposition like в?

Вечером is the instrumental case of вечер. In Russian, some time expressions use the bare instrumental case to mean “in/at [time]”:

утром – in the morning
днём – in the daytime / during the day
вечером – in the evening
ночью – at night

You could theoretically say сегодня вечером or сегодня в вечернее время, but вечером alone, in the instrumental, already carries the meaning “in the evening”, so no preposition is needed.

What is the difference between мы собираемся смотреть and мы будем смотреть?

Both refer to a future action, but with different nuances:

мы собираемся смотреть
- Literally: we are gathering ourselves / getting ready to watch → idiomatically: we are going to watch / we intend to watch.
- Emphasizes intention / plan.
- Very close to English be going to.
мы будем смотреть
- Literally: we will watch (simple future of смотреть).
- Neutral statement about the future; it doesn’t highlight the “plan” aspect as strongly.

In conversation, мы собираемся смотреть sounds a bit more like: “That’s what we’re planning / that’s the plan for tonight.”

Why does собираемся have the -ся ending? What is the difference between собирать and собираться?

The ending -ся is a reflexive/“self” marker in Russian.

собирать (without -ся)
- Basic meaning: to gather, collect, assemble (something)
- Example: собирать книги – to collect books.
собираться (with -ся)
- Literal: to gather oneself / to get together
- Common meanings:
  1. To get ready / to be about to do something
    - Мы собираемся смотреть фильм. – We are going to watch a film.
  2. To get together, to assemble (as people)
    - Мы собираемся у друзей. – We’re meeting / gathering at friends’.

In this sentence, собираемся means we are planning / going to, not physically collecting something.

What case is интересный фильм in, and why is it not интересного фильма?

Интересный фильм is in the accusative case, functioning as the direct object of смотреть (“to watch”).

For inanimate masculine nouns (like фильм) in Russian, the accusative singular form is identical to the nominative:

Nominative: интересный фильм – an interesting film (subject)
Accusative: смотреть интересный фильм – to watch an interesting film (object)

You would use интересного фильма in genitive contexts, for example:

у меня нет интересного фильма – I don’t have an interesting film.

So интересный фильм here is correct because it’s a direct object in the accusative.

Why is there no article or preposition before интересный фильм, like a film in English?

Russian has no articles (no direct equivalent of a / an / the). The noun phrase интересный фильм can mean:

an interesting film
the interesting film
some interesting film

The exact nuance (a/the/some) is understood from context, not from a separate word.
Also, Russian doesn’t need a preposition here; смотреть directly takes its object in the accusative:

смотреть фильм – to watch a film
смотреть интересный фильм – to watch an interesting film

Why is it дома and not в доме or домой? What’s the difference?

These three forms express different ideas:

дома
- Means at home (location, where?).
- Мы смотрим фильм дома. – We are watching a film at home.
в доме
- Literally in the house, more physical/locational and not always “at home” in the personal sense.
- Could mean “in a certain building/house”.
- Мы живём в доме номер пять. – We live in house number five.
домой
- Means (to) home, direction (where to?):
- Мы идём домой. – We are going home.

In your sentence, the meaning is clearly at home, so дома is the natural choice.

Can the word order change, for example: Сегодня вечером дома мы собираемся смотреть интересный фильм? How flexible is the word order?

Russian word order is more flexible than English, but not completely free.

All of these are grammatically possible:

Сегодня вечером мы собираемся смотреть интересный фильм дома. (original)
Сегодня вечером мы дома собираемся смотреть интересный фильм.
Сегодня вечером дома мы собираемся смотреть интересный фильм.

The basic information (who, what, where, when) stays the same, but word order can:

change what is emphasized
affect how natural / neutral the sentence sounds.

The original sentence is the most neutral and natural:

time (Сегодня вечером)
subject + verb (мы собираемся)
what (смотреть интересный фильм)
where (дома).

Putting дома earlier (e.g. Сегодня вечером дома мы…) gives a little extra emphasis to at home (“Tonight at home, we are going to…”), which is fine but slightly more marked.

Could we say посмотреть instead of смотреть here, as in мы собираемся посмотреть интересный фильм дома? What’s the difference?

Yes, you can say:

Мы собираемся смотреть интересный фильм дома.
Мы собираемся посмотреть интересный фильм дома.

Both are correct, but aspect changes the nuance:

смотреть – imperfective aspect
- Focus on the process / duration: “We’re going to be watching an interesting film at home.”
- Neutral description of the plan/activity.
посмотреть – perfective aspect
- Focus on the completed action / result: “We’re going to (have a) watch of an interesting film at home” → we plan to watch it through / finish it.
- Often implies doing it once, to completion.

In everyday speech, both are common; смотреть sounds like focusing on the activity, посмотреть a bit more on the fact of getting it watched.

Is the pronoun мы necessary here, or can it be omitted?

Russian is a pro‑drop language: the subject pronoun can be omitted if the verb ending makes it clear.

So you could say:

Сегодня вечером собираемся смотреть интересный фильм дома.

The verb ending -емся in собираемся clearly indicates мы (“we”), so the meaning is still obvious.

Including мы is:

a bit more explicit and typical in neutral speech,
helpful when you want to emphasize we (as opposed to someone else).

Omitting мы is common in informal speech and doesn’t sound wrong.