На обед я сварила суп с вермишелью.

Not literally. In Russian, на + accusative is often used in set expressions for meals:

• на завтрак = for breakfast
• на обед = for lunch
• на ужин = for dinner/supper

So На обед я сварила суп... means I cooked soup for lunch or For lunch, I cooked soup...

A nearby expression is к обеду, but that means more like by lunchtime or for lunchtime, to be ready by then.

Because after на in this kind of expression, Russian uses the accusative.

Here на обед expresses purpose/occasion: the soup was made for lunch.

You can think of it as a fixed meal-time pattern:

• на завтрак
• на обед
• на ужин

Since обед is a masculine inanimate noun, its accusative singular looks the same as the nominative singular, so you see обед, not a different form.

Because Russian has no articles.

So суп can mean:

• soup
• a soup
• the soup

The context tells you which one is meant. In this sentence, English would normally say I cooked soup or I cooked some soup.

Сварила is the past tense of сварить.

Here it means cooked / made by boiling. With soup, this is very natural, because soup is something you boil.

So сварила суп is basically:

• cooked soup
• made soup

It is often more specific than the broad verb приготовила (prepared / made).

Because the speaker is female.

In the Russian past tense, verbs agree with gender and number:

• я сварил = I cooked (male speaker)
• я сварила = I cooked (female speaker)
• мы сварили = we cooked

So this sentence tells you that the person speaking is a woman.

This is about aspect, which is very important in Russian.

• варила = imperfective
• сварила = perfective

Here сварила shows a completed result: the soup got cooked.

So:

• Я варила суп = I was cooking soup / I used to cook soup / I cooked soup (focus on process)
• Я сварила суп = I cooked the soup / I managed to cook the soup (focus on completion)

In this sentence, the natural idea is I made soup for lunch, so the completed perfective verb сварила fits well.

Yes, суп is the direct object, so it is in the accusative.

But for many masculine inanimate singular nouns, the accusative is the same as the nominative. So:

• nominative: суп
• accusative: суп

That is why the form does not change.

Compare with a feminine noun, where the accusative often looks different:

• каша → кашу

Here с means with, and in that meaning it normally takes the instrumental case.

So:

• с вермишелью = with vermicelli / with noodles

The base noun is вермишель, and its instrumental singular form is вермишелью.

So the structure is:

• с + instrumental

Examples:

• чай с лимоном = tea with lemon
• бутерброд с сыром = sandwich with cheese
• суп с вермишелью = soup with vermicelli

Вермишель means vermicelli or thin noodles.

In everyday translation, суп с вермишелью is often best understood as:

• noodle soup
• soup with thin noodles

It is a feminine noun in Russian, even though it ends in a soft sign.

Not always. Russian often drops subject pronouns when the meaning is clear from the verb.

So both are possible:

• На обед я сварила суп с вермишелью.
• На обед сварила суп с вермишелью.

Including я can make the subject a little more explicit or contrastive. For example, it may sound like As for me, I made soup for lunch.

Yes, Russian word order is flexible.

This version puts На обед first, which sets the scene: For lunch...

Other possible orders include:

• Я сварила на обед суп с вермишелью.
• Суп с вермишелью я сварила на обед.

The basic meaning stays the same, but the emphasis changes.

A very natural neutral order is:

• Я сварила суп с вермишелью на обед.
• На обед я сварила суп с вермишелью.

The version you have is good and natural.

Yes.

• сварила = specifically cooked by boiling
• приготовила = prepared / made in a broader sense

So:

• На обед я сварила суп с вермишелью. = For lunch, I cooked soup with vermicelli.
• На обед я приготовила суп с вермишелью. = For lunch, I prepared/made soup with vermicelli.

Both are natural, but сварила is more specific and vivid for soup.

The main stresses are:

• на обЕд
• я сварИла
• суп
• с вермишЕлью

So you can read it as:

На обЕд я сварИла суп с вермишЕлью.

That will give you a good natural pronunciation pattern.