Après le dîner, nous allons nous installer sur le canapé pour regarder le film.

Here, dîner is a noun meaning dinner/the evening meal, so French normally uses an article: le dîner.

• après le dîner = after dinner
• après avoir dîné = after having dinner

You may sometimes see après dîner, but après le dîner is the most straightforward everyday form for this meaning.

Après le dîner is an introductory time phrase, so the comma helps separate it from the main clause. In English, this is very common too: After dinner, we’re going to...

In French, the comma is natural here, but it is not absolutely required in every case.

Aller + infinitive is the French near future, used very often for plans, intentions, or something expected to happen soon.

• nous allons nous installer = we’re going to settle in
• nous nous installerons = we will settle in

Both are possible, but nous allons + infinitive often sounds more conversational and immediate.

They do two different jobs:

• the first nous is the subject pronoun: we
• the second nous is the reflexive pronoun that goes with s’installer

So the structure is:

• nous allons = we are going
• nous installer = to settle ourselves / to get settled

French uses reflexive verbs more often than English does.

Here, s’installer does not mean to install oneself in a literal technical sense. It means something like:

• to settle in
• to get comfortable
• to make oneself comfortable
• to sit down and get ready

So nous allons nous installer sur le canapé suggests getting comfortable on the couch before watching the movie.

With aller + infinitive, the reflexive pronoun stays attached to the infinitive, not to aller.

So French says:

• nous allons nous installer
• je vais me coucher
• ils vont se préparer

Not:

• nous nous allons installer for this meaning

That word order is a very common pattern in French.

Sur means on, and with furniture like canapé it is the normal choice for sitting or settling down on it.

• sur le canapé = on the sofa/couch

An English speaker may not find this surprising here, but it is worth noticing that French often uses prepositions in its own fixed way, so it is best to learn them together with the expression.

The definite article le points to something specific or already understood from the context.

• le canapé = the sofa (the one we mean, probably the one in the room)
• le film = the film/movie (a particular one)

If the sentence said un film, it would sound more like some movie / a movie, not a specific one.

Pour + infinitive is a very common way to express purpose in French.

So:

• pour regarder le film = in order to watch the film
• more naturally in English: to watch the film

This is one of the easiest and most useful French patterns to learn.

Because regarder means to watch / to look at, while voir means to see.

• regarder un film = to watch a movie
• voir un film = to see a movie

Both can be correct in some contexts, but regarder emphasizes the action of watching it.

In standard modern French in France, dîner usually means dinner, the evening meal.

But there is regional variation:

• in France: déjeuner = lunch, dîner = dinner
• in some other French-speaking regions, especially parts of Canada: dîner can mean lunch

So in this sentence, the intended meaning depends on the variety of French, but for most learners of standard French from France, dîner here will be understood as dinner.

Yes. A few natural alternatives are possible, depending on style and nuance:

• Après le dîner, nous nous installerons sur le canapé pour regarder le film.
• Après le dîner, on va s’installer sur le canapé pour regarder le film.

The second version with on is especially common in spoken French and means the same as nous in everyday conversation.