На завтрак я сделал омлет с ветчиной, взял кусок батона и выпил стакан кефира.

На завтрак is the normal Russian way to say for breakfast.

• на
  • accusative is often used for something intended for a meal:
    • на завтрак = for breakfast
    • на обед = for lunch
    • на ужин = for dinner

So in this sentence, На завтрак sets the context: For breakfast, I...

It is not translated word-for-word into natural English. A literal gloss would be something like for breakfast rather than on breakfast.

Because на can take different cases depending on meaning.

Here, на завтрак means for breakfast / as breakfast, so завтрак is in the accusative case. Since завтрак is an inanimate masculine noun, its accusative form is the same as the nominative:

• nominative: завтрак
• accusative: завтрак

If you said на завтраке, that would mean something more like at breakfast or during breakfast, with a different nuance.

In Russian past tense, verbs agree with the subject in gender and number.

Since the subject is я, the verb form tells you whether the speaker is male or female:

• male speaker: сделал, взял, выпил
• female speaker: сделала, взяла, выпила

So this sentence was said by a male speaker. If a woman said it, the sentence would be:

На завтрак я сделала омлет с ветчиной, взяла кусок батона и выпила стакан кефира.

Russian usually does not repeat the subject if it stays the same.

So:

• На завтрак я сделал омлет с ветчиной, взял кусок батона и выпил стакан кефира.

means:

• For breakfast, I made an omelet with ham, took a piece of bread, and drank a glass of kefir.

Repeating я before each verb would sound unnecessary in most contexts.

Yes. In everyday Russian, сделать can mean to make / prepare something, including food.

So сделал омлет is natural and means made an omelet.

Other possible verbs are:

• приготовил омлет = prepared an omelet
• пожарил омлет = fried an omelet

But сделал омлет is completely normal in casual speech.

Because омлет is the direct object of сделал.

The verb сделать answers made what? → омлет

Since омлет is an inanimate masculine noun, its accusative form is the same as the nominative:

• nominative: омлет
• accusative: омлет

So сделал омлет is exactly what you would expect.

After с meaning with, Russian normally uses the instrumental case.

So:

• ветчина = ham
• instrumental: ветчиной

That is why you get:

• омлет с ветчиной = omelet with ham

Some more examples:

• чай с сахаром = tea with sugar
• бутерброд с сыром = sandwich with cheese
• кофе с молоком = coffee with milk

Not exactly. Батон usually means a long white loaf, often the standard soft white bread loaf common in Russian-speaking countries.

So кусок батона is something like:

• a piece of white loaf
• a slice/chunk of bread

It is not the general word for all bread. The general word is хлеб.

Compare:

• хлеб = bread in general
• батон = a specific kind of white loaf

This is a very common Russian pattern: when you talk about a piece, glass, cup, bottle, etc. of something, the second noun is usually in the genitive case.

So:

• кусок = a piece
• батон → батона in the genitive

Thus:

• кусок батона = a piece of loaf/bread

The same pattern appears in:

• стакан воды = a glass of water
• чашка чая = a cup of tea
• бутылка молока = a bottle of milk

Because взял literally means took. The sentence is describing the speaker’s breakfast actions in sequence:

1. сделал омлет
2. взял кусок батона
3. выпил стакан кефира

Russian often narrates actions this way, and взял кусок батона can sound natural in context, even if English might more naturally say had some bread or ate a piece of bread.

If the speaker wanted to emphasize eating it, they could say:

• съел кусок батона = ate a piece of bread

But взял is still grammatically and stylistically fine.

No. выпил стакан кефира means drank a glass of kefir, not the physical glass.

This is the same as in English:

• drink a cup of tea
• eat a plate of soup is not natural English, but the idea of container words is similar

In Russian, стакан here means a glassful / a glass serving of something.

And again, the thing inside the container goes into the genitive:

• стакан кефира = a glass of kefir

Because of the quantity/container pattern:

• стакан чего? = a glass of what?
• answer: кефира

So:

• кефир = kefir
• genitive: кефира

This is the same structure as:

• стакан воды = a glass of water
• чашка кофе = a cup of coffee
• бутылка сока = a bottle of juice

They are perfective because the sentence presents the actions as completed whole events.

• сделал = made / finished making
• взял = took
• выпил = drank up / drank

This is very natural when listing completed actions in a narrative.

If you used imperfective verbs, the meaning would shift more toward process, habit, or background description:

• делал = was making / used to make
• брал = was taking / used to take
• пил = was drinking / used to drink

So the perfective verbs fit a one-time completed breakfast description.

Yes, often you could.

Russian often drops personal pronouns when the subject is clear from the verb form or context. So this would also work:

На завтрак сделал омлет с ветчиной, взял кусок батона и выпил стакан кефира.

However, keeping я is also natural. It may sound a bit clearer or slightly more emphatic.

Yes, Russian word order is flexible.

This sentence is neutral and natural:

На завтрак я сделал омлет с ветчиной, взял кусок батона и выпил стакан кефира.

But other orders are also possible, depending on emphasis:

• Я на завтрак сделал омлет с ветчиной, взял кусок батона и выпил стакан кефира.
• Омлет с ветчиной я сделал на завтрак, взял кусок батона и выпил стакан кефира.

The original version is good because it starts with the time/context phrase На завтрак, which frames the whole sentence.

Because this sentence contains a series of coordinated verbs, and there is already a comma separating earlier parts of the list:

• сделал омлет с ветчиной, взял кусок батона и выпил стакан кефира

Russian punctuation often uses commas in lists of actions just as English does.

So the speaker did three things:

1. made an omelet with ham,
2. took a piece of bread,
3. drank a glass of kefir.

The comma helps separate the first action from the following coordinated actions.

Usually кефир behaves like an uncountable drink, similar to milk or yogurt drink in English.

So you normally say things like:

• пить кефир = to drink kefir
• стакан кефира = a glass of kefir
• купить кефир = to buy kefir

You would not usually count it directly as separate units unless you mean containers:

• две бутылки кефира = two bottles of kefir

It is mostly natural everyday Russian.

A native speaker might also say slightly different versions, for example:

• На завтрак я приготовил омлет с ветчиной, съел кусок батона и выпил стакан кефира.
• На завтрак я сделал омлет с ветчиной, съел кусок хлеба и выпил стакан кефира.

The only slightly notable point is взял кусок батона: it literally means took a piece of bread, which is understandable and possible, though in some contexts съел кусок батона might sound more explicit and natural if the point is what he actually ate. Still, the original sentence is perfectly normal Russian.