Learn Hardcore French: Maintenant que le dîner est prêt, nous pouvons manger.

You need que because French uses it to link the idea to the following clause. English does the same in a different way with that inside now that.

A learner mistake would be trying to say:

Maintenant le dîner est prêt... for Now that dinner is ready...

That sounds wrong for this meaning. You need maintenant que.

Why is it le dîner and not just dîner?

French often uses an article where English does not.

So even though English says dinner, French normally says le dîner.

This is very common:

le dîner = dinner
le café = coffee
la maison = home/house, depending on context

French generally prefers nouns to have an article unless there is a specific reason not to use one.

So le dîner est prêt is the natural way to say dinner is ready.

Why is it est prêt? Why does prêt come after the verb?

In French, adjectives can come either before or after a noun, but after être they usually come after the verb, just like in English.

Here:

est = is
prêt = ready

So:

le dîner est prêt = the dinner is ready

This is a normal pattern:

Le repas est bon = the meal is good
La table est propre = the table is clean

You would not say le dîner prêt est.

Why is it prêt and not prête?

Prêt agrees with le dîner, which is masculine singular.

Agreement works like this:

masculine singular: prêt
feminine singular: prête
masculine plural: prêts
feminine plural: prêtes

Because dîner is masculine, the correct form is prêt.

Compare:

Le dîner est prêt.
La soupe est prête.

Why is it nous pouvons and not nous pouvons mangerons or another future form?

French often uses the present tense where English also uses the present or where English might sometimes choose a future-related idea.

Here, nous pouvons manger means we can eat.

pouvons = can / are able to
manger = eat

You do not use a second conjugated verb after pouvons. After a modal verb like pouvoir, the next verb stays in the infinitive:

nous pouvons manger = we can eat
je peux venir = I can come
ils peuvent partir = they can leave

So mangerons would be wrong here because after pouvons, you need manger, not a future tense form.

Why does French use the present tense in both parts of the sentence?

Because both parts describe a present situation:

le dîner est prêt = dinner is ready
nous pouvons manger = we can eat

This is very natural in French. Once dinner is ready, eating is possible now, so the present tense fits both clauses.

French does not need a future tense here. It is not talking about some distant future; it is talking about what is true at this moment.

Could I say on peut manger instead of nous pouvons manger?

Yes. In everyday spoken French, on peut manger is very common and often sounds more natural in casual conversation.

Compare:

Nous pouvons manger. = more formal or careful
On peut manger. = very common in speech

Both mean we can eat in this context.

A learner should know that:

nous is standard and fully correct
on is extremely common in modern spoken French for we

Is there a reason for the comma?

Yes. The sentence begins with a subordinate clause:

Maintenant que le dîner est prêt

Then it moves to the main clause:

nous pouvons manger

The comma helps separate these two parts, just as in English:

Now that dinner is ready, we can eat.

In short:

first clause gives the condition/background
second clause gives the result

The comma is normal and helpful here.

How do you pronounce dîner and prêt?

A few useful points:

dîner has a long ee-like sound in the first syllable because of î
prêt has an open e sound, roughly like preh

Very roughly for an English speaker:

dîner ≈ dee-nay
prêt ≈ preh

A few details:

The î in dîner does not usually change the basic modern pronunciation much compared with i, but it reflects spelling/history.
The final t in prêt is normally pronounced.

So the phrase sounds roughly like:

Maintenant que le dîner est prêt ≈ man-teuh-nan kuh luh dee-nay eh preh

That is only approximate, but it can help at first.

Why is it le dîner est prêt and not le dîner a prêt or something with avoir?

French uses être with many adjectives to describe a state.

So:

être prêt = to be ready

That is why the sentence uses:

le dîner est prêt

not a prêt

Compare:

Il est fatigué. = He is tired.
La chambre est propre. = The room is clean.
Le dîner est prêt. = Dinner is ready.

Use être when you are describing what something is like or what state it is in.

Can maintenant que be replaced by something else?

Sometimes, yes, but the meaning or tone may change slightly.

Possible alternatives include:

Puisque le dîner est prêt, nous pouvons manger.
Comme le dîner est prêt, nous pouvons manger.

But they are not exactly the same in feel.

maintenant que focuses on the idea that the situation is true now
puisque often means since or because, with a sense that the reason is already known or obvious
comme can mean since/as, often at the beginning of a sentence

So maintenant que is the best choice if you specifically want now that.

Is manger just the basic infinitive here? Why isn’t it changed?

Yes. Manger is the infinitive, and it stays in the infinitive because it follows pouvoir.

This pattern is very important:

pouvoir + infinitive
vouloir + infinitive
devoir + infinitive
aimer + infinitive in some contexts

Examples:

Je peux manger. = I can eat.
Nous voulons partir. = We want to leave.
Tu dois travailler. = You must work.

So in nous pouvons manger, only pouvoir is conjugated. Manger stays in its base form.

Would a French speaker really say this sentence in everyday life?

Yes, it is perfectly natural and correct.

That said, in casual speech, people might also say things like:

Le dîner est prêt, on peut manger.
Maintenant que c’est prêt, on peut manger.
Le repas est prêt, on mange ?

So your sentence is good, natural, and clear, but spoken French often prefers on over nous, and sometimes uses shorter phrasing.