Je mange des amandes grillées au petit-déjeuner.

Because manger is a normal verb that conjugates by itself. In French, je mange simply means I eat or I am eating, depending on context.

French usually does not need a separate am/are/is + -ing structure the way English does. So:

• Je mange = I eat / I am eating
• Tu manges = you eat / you are eating

So in this sentence, mange is the 1st person singular present tense form of manger.

Here, des means some.

So des amandes means some almonds.

It is the usual plural article for an unspecified number of things. Compare:

• une amande = an almond
• les amandes = the almonds
• des amandes = some almonds

In this sentence, the speaker is not talking about specific almonds already known to the listener, so des is the natural choice.

In French, adjectives often come after the noun, unlike English.

So:

• amandes grillées literally follows the French order almonds grilled
• natural English order is grilled almonds

This is very common in French. For example:

• une voiture rouge = a red car
• des légumes frais = fresh vegetables

Some adjectives come before the noun, but grillé/grillée(s) normally comes after.

Because the adjective must agree with the noun it describes.

Here, amandes is:

• feminine: une amande
• plural: des amandes

So the adjective grillé has to match:

• masculine singular: grillé
• feminine singular: grillée
• masculine plural: grillés
• feminine plural: grillées

Since amandes is feminine plural, French uses grillées.

Because nouns in French have grammatical gender, and amande happens to be a feminine noun.

You learn it as:

• une amande

That feminine gender affects the article and adjective agreement:

• une amande grillée
• des amandes grillées

This gender is grammatical, not biological. Objects and foods can also be masculine or feminine in French.

Au petit-déjeuner means for breakfast / at breakfast time.

It tells you when or on what occasion the speaker eats the almonds.

The expression comes from:

• à + le = au

So literally, au petit-déjeuner is at the breakfast in form, though in natural English we usually say for breakfast or at breakfast.

Examples:

• Je bois du café au petit-déjeuner. = I drink coffee for breakfast.
• Il mange du pain au petit-déjeuner. = He eats bread at breakfast.

Because à le contracts in French.

The contraction is:

• à + le = au
• à + les = aux

So French says:

• au petit-déjeuner not
• à le petit-déjeuner

This kind of contraction is mandatory.

Because petit-déjeuner is a fixed compound noun meaning breakfast.

French often uses hyphens in compound words. So as a noun, you will often see:

• le petit-déjeuner

You may also see some spelling variation in less formal contexts, but petit-déjeuner with a hyphen is a standard and very common form.

Also note that petit déjeuner can sometimes refer to the verb phrase to have breakfast in certain contexts, but in your sentence le petit-déjeuner is clearly the noun breakfast.

It can mean either one in French, because the present tense often covers both ideas.

So depending on context:

• Je mange des amandes grillées au petit-déjeuner. can mean
  I eat grilled almonds for breakfast (habit)
• It could also mean
  I’m eating grilled almonds at breakfast (right now), if the context makes that clear

In most cases, without extra context, learners will usually understand this sentence as a habitual statement: something the person eats for breakfast in general.

Yes, absolutely.

French often uses prendre with meals, drinks, and food choices in a way that sounds broader than eat in English.

So both are possible:

• Je mange des amandes grillées au petit-déjeuner. = I eat grilled almonds for breakfast.
• Je prends des amandes grillées au petit-déjeuner. = I have grilled almonds for breakfast.

Mange focuses more directly on the act of eating.
Prends can sound a bit more like have or take as part of a meal.

Because before a plural noun, the indefinite plural article is des, not de amandes.

So:

• des amandes = some almonds

French does use de instead of des in some situations, but not here. For example:

1. After a negative verb

   • Je ne mange pas d’amandes. = I do not eat almonds.

2. Often before a plural adjective + noun

   • de petites amandes not usually
   • des petites amandes

But in your sentence, the adjective comes after the noun, so des amandes grillées is correct.

A careful approximate pronunciation is:

zhuh mahnzh day zah-mahn-d gree-yay oh puh-tee day-zhuh-nay

A few useful notes:

• Je sounds like zhuh
• mange rhymes roughly with orange without the final j sound in English
• des amandes may have a light linking sound in fluent speech
• grillées has two syllable parts at the end: gree-yay
• petit-déjeuner is pronounced roughly puh-tee day-zhuh-nay

The exact sounds depend on accent, but those approximations can help you get started.

Not always.

In France, le petit-déjeuner is the normal word for breakfast.

In some other French-speaking regions, especially parts of Switzerland and Belgium, you may also hear:

• déjeuner = breakfast
• dîner = lunch
• souper = dinner

But in standard French as taught to most learners, especially France French:

• petit-déjeuner = breakfast
• déjeuner = lunch
• dîner = dinner

So your sentence is perfectly standard and widely understood.

Normally, no.

French usually requires an explicit subject pronoun with a conjugated verb:

• Je mange
• Tu manges
• Il mange

Unlike Spanish or Italian, French does not usually drop the subject pronoun in ordinary speech or writing.

So Je mange des amandes grillées au petit-déjeuner is the normal complete form.