Для супа я нарезала шпинат и сельдерей, а потом добавила немного сливок.

Для супа means for the soup. The preposition для always requires the genitive case, so суп becomes супа.

Starting the sentence this way puts the purpose first: As for the soup / For the soup, I sliced... In English we might be more likely to say I sliced spinach and celery for the soup, but Russian often moves this kind of phrase to the front for emphasis or context.

Because для takes the genitive case.

• nominative: суп
• genitive: супа

So:

• для супа = for the soup

This is a very common pattern in Russian:

• для друга = for a friend
• для работы = for work
• для детей = for children

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

Here the subject is я, and the speaker is female, so the verbs are feminine:

• я нарезала = I sliced
• я добавила = I added

If the speaker were male, you would say:

• я нарезал
• я добавил

If it were we, then:

• мы нарезали
• мы добавили

These are past tense perfective verbs, which is very natural when describing completed steps in cooking.

• нарезала = sliced up / cut up
• добавила = added

The perfective aspect shows that each action was completed as a finished step:

1. I sliced the spinach and celery.
2. Then I added some cream.

That fits recipe-style narration very well.

They are the direct objects of the verb, so they are in the accusative case. But for many inanimate masculine nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• шпинат: nominative = accusative
• сельдерей: nominative = accusative

That is why you see:

• нарезала шпинат
• нарезала сельдерей

and not a visibly different ending.

Because немного requires the genitive case.

The noun сливки is a special word: it is normally used only in the plural in Russian, even though in English cream is usually treated as singular or uncountable.

So the dictionary form is:

• сливки = cream

But after немного, you need the genitive plural:

• немного сливок = a little/some cream

This is a very useful pattern:

• немного воды = a little water
• немного сахара = a little sugar
• немного денег = a little money

Some Russian nouns are plural-only nouns. They behave grammatically like plurals even when English uses a singular or uncountable noun.

Сливки is one of those words. So Russian says:

• сливки
• много сливок
• немного сливок

Even though in English we simply say cream.

Other common plural-only nouns include:

• ножницы = scissors
• часы = clock/watch
• деньги = money

Потом means then / afterwards.

The conjunction а here does not strongly mean but. In many sentences, а simply links one step to the next, often with a slight sense of transition or contrast between actions.

So:

• ..., а потом добавила немного сливок
  = ..., and then added some cream

In English, translating а as and is often more natural in this kind of sentence.

Because а connects two coordinated parts of the sentence, and Russian normally places a comma before а.

So:

• Для супа я нарезала шпинат и сельдерей, а потом добавила немного сливок.

This comma is standard Russian punctuation.

Yes. Russian word order is flexible, and changing it usually changes the emphasis, not the basic meaning.

For example, you could also say:

• Я нарезала шпинат и сельдерей для супа, а потом добавила немного сливок.

This sounds a bit more neutral in structure.

But:

• Для супа я нарезала...

puts for the soup first, setting the context right away.

So both are possible; the original sentence just emphasizes the purpose at the beginning.

Нарезать usually means to cut up into pieces, often to slice/chop up something for cooking.

So in this sentence, нарезала шпинат и сельдерей suggests preparing the ingredients by cutting them into smaller pieces, not just making one cut.

That is why translations like these can all work depending on context:

• I cut up the spinach and celery
• I chopped the spinach and celery
• I sliced the spinach and celery

No. Russian does not have articles.

So words like:

• суп
• шпинат
• сельдерей
• сливки

do not automatically tell you a soup vs the soup, some spinach vs the spinach. You understand that from context.

That is why Для супа can mean for soup or for the soup, depending on the situation.