A colazione mangio yogurt con cereali e pera.

A colazione is an idiomatic way to say for breakfast or literally at breakfast.

In Italian, meals are often introduced this way:

• a colazione = for breakfast
• a pranzo = for lunch
• a cena = for dinner

So A colazione mangio... means For breakfast, I eat...

You may also hear Per colazione, which is also correct and very common. The version with a is just a very natural Italian way to express it.

Mangio is the first person singular form of mangiare (to eat) in the present tense.

So:

• io mangio = I eat
• tu mangi = you eat
• lui/lei mangia = he/she eats

In this sentence, the subject io is not stated because Italian often leaves subject pronouns out when the verb already makes the subject clear.

So mangio by itself already means I eat.

Italian often drops subject pronouns when they are not needed.

Because mangio clearly means I eat, adding io is usually unnecessary.

So:

• A colazione mangio yogurt con cereali e pera. = normal, natural
• A colazione io mangio yogurt con cereali e pera. = possible, but more emphatic

You would usually include io only if you want contrast or emphasis, for example:

• Io mangio yogurt, lui mangia uova.
  I eat yogurt, he eats eggs.

Italian often leaves out the article when talking about food in a general, list-like way, especially after verbs like mangiare and bere.

So this is very natural:

• mangio yogurt
• bevo caffè
• mangio pasta

If you say lo yogurt, it usually sounds more specific:

• Mangio lo yogurt che ho comprato ieri.
  I’m eating the yogurt I bought yesterday.

Also, yogurt is usually masculine in Italian, so with an article it is normally:

• lo yogurt

Con cereali means with cereal in a general sense, as an ingredient or accompaniment.

Italian often omits the article when speaking generally about foods:

• yogurt con cereali
• pane con marmellata
• pasta con pomodoro

If you say con i cereali, it sounds more specific, as if you mean particular cereals already known in the context.

So:

• con cereali = with cereal / with some cereal, generally
• con i cereali = with the cereal(s), specific ones

In Italian, cereali is the normal word used for cereal in the breakfast-food sense.

Even though English often uses singular cereal, Italian commonly uses the plural:

• i cereali = cereal / breakfast cereal

The singular cereale usually refers more to a cereal grain or the category of grain itself, rather than a bowl of breakfast cereal.

So yogurt con cereali is the natural phrase.

This sentence presents breakfast foods in a simple list, so Italian can omit the article:

• yogurt
• cereali
• pera

That sounds like yogurt with cereal and pear as breakfast items.

However, una pera is also possible if you want to emphasize one pear as a countable item:

• A colazione mangio uno yogurt con cereali e una pera.

That version may sound a little more explicit and is also very natural.

So the difference is roughly:

• pera = pear, as a food item in a list
• una pera = one pear

Yes, pera is singular on purpose. It suggests one pear, or simply pear as one of the breakfast items.

If you wanted to say pears, you would use the plural:

• pere

So:

• pera = pear
• pere = pears

In food descriptions, Italian often uses singular nouns naturally when referring to a single item eaten as part of a meal.

Con means with.

So yogurt con cereali means yogurt with cereal.

This shows that the cereal goes together with the yogurt. Then e pera adds another item to the breakfast:

• yogurt con cereali = yogurt with cereal
• e pera = and pear

Without con, the meaning would be more like a simple list of separate items.

It connects pera to the previous food phrase.

So the sentence groups like this:

• A colazione
• mangio
• [yogurt con cereali] e [pera]

That means the speaker eats:

1. yogurt with cereal
2. pear

So con cereali belongs with yogurt, not with pera.

Yes. Italian word order is fairly flexible.

The sentence begins with A colazione to set the context first: For breakfast...

But you could also say:

• Mangio yogurt con cereali e pera a colazione.

That is also grammatically correct. It just sounds a little different in focus.

Compare:

• A colazione mangio yogurt con cereali e pera.
  Focus first on breakfast
• Mangio yogurt con cereali e pera a colazione.
  Focus first on what I eat

The version with A colazione at the beginning is very natural.

It is similar, but the pronunciation may vary depending on the speaker.

In standard Italian, yogurt is a borrowed word, and many speakers pronounce it approximately like:

• YO-gurt or YO-gurt with an Italian accent

The important thing for learners is mainly to recognize that it is the same word as English yogurt.

Also, the word is generally invariable in Italian, meaning it usually does not change in the plural:

• uno yogurt
• due yogurt

Yes, but it changes the structure.

Fare colazione means to have breakfast. So you can say:

• Faccio colazione con yogurt, cereali e pera.
  I have breakfast with yogurt, cereal, and pear.

That is perfectly natural.

Your original sentence uses mangio because it directly says what the person eats:

• A colazione mangio yogurt con cereali e pera.
  For breakfast I eat yogurt with cereal and pear.

Both are correct; they just express the idea differently.