Для борща нужны капуста и свёкла, а сверху я люблю добавлять укроп и петрушку.

Because the preposition для always requires the genitive case. The dictionary form is борщ, but after для it becomes борща.

• борщ → nominative
• для борща → genitive

This is a very common pattern:

• для супа
• для салата
• для чая

Нужны means are needed / are necessary. It is the short form of the adjective нужный.

In Russian, short-form adjectives are often used as the main predicate of a sentence:

• Капуста нужна. = Cabbage is needed.
• Овощи нужны. = Vegetables are needed.

So Для борща нужны капуста и свёкла literally means something like For borscht, cabbage and beetroot are needed.

In the present tense, Russian usually leaves out the verb to be when it links the subject and predicate.

So Russian says:

• Капуста нужна.

not:

• Капуста есть нужна.

The word есть can mean there is/there are, but it is not normally used here as a simple present-tense is/are.

Because the thing that is needed is капуста и свёкла together. That is a compound subject, so Russian treats it as plural.

Compare:

• Для борща нужна капуста. = Cabbage is needed.
• Для борща нужны капуста и свёкла. = Cabbage and beetroot are needed.

So нужна would be for one feminine noun, but нужны is used for two items together.

Because in this construction they are not direct objects. They are the things that are needed, so they function as the grammatical subject of the sentence and stay in the nominative.

That is different from the second clause:

• я люблю добавлять укроп и петрушку

Here, укроп and петрушку are direct objects of добавлять, so they go into the accusative.

Russian often uses the singular when naming ingredients or foods in a general way.

So:

• капуста
• свёкла
• укроп
• петрушка

all name the ingredient as a substance or category, not necessarily one single physical item. This is very natural in recipes and food talk.

English can do something similar too: You need cabbage, beetroot, dill, and parsley.

А often connects two related ideas while also showing a shift of focus or a mild contrast.

Here the first part is about what is needed for the dish, and the second part shifts to the speaker’s personal preference:

• Для борща нужны...
• а сверху я люблю добавлять...

So а feels natural: and as for the top / and then on top, I like to add...

If you used и, it would sound more like simple addition and a little less nuanced.

Literally, сверху means from above / on top. In food contexts, it often means on top or as a topping/garnish.

So here it means something like:

• on top
• over it
• as a garnish

It is not about physical location in a broad sense; it is specifically about adding something on top of the finished dish.

Russian commonly uses любить + infinitive to mean to like/love doing something.

So:

• Я люблю добавлять... = I like to add...

This is a very common pattern:

• Я люблю читать. = I like reading.
• Он любит готовить. = He likes cooking.

Because the speaker is talking about a general habit or preference, not one single completed action.

• добавлять = imperfective, focusing on the process/habit
• добавить = perfective, focusing on a completed act

So я люблю добавлять means I like adding / I like to add in general.

If you said люблю добавить, that would usually sound wrong or at least unnatural in this context.

Because добавлять takes a direct object in the accusative case.

• петрушка is feminine, so accusative singular becomes петрушку
• укроп is masculine inanimate, so its accusative singular looks the same as the nominative: укроп

So:

• nominative: укроп, петрушка
• accusative: укроп, петрушку

This is a very important pattern in Russian.

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

The original sentence is natural and neutral:

• Для борща нужны капуста и свёкла, а сверху я люблю добавлять укроп и петрушку.

But you could also hear things like:

• Я люблю сверху добавлять укроп и петрушку.
• Укроп и петрушку я люблю добавлять сверху.

These versions are possible, but they highlight different parts of the sentence.

For learners, it is best to treat ё as important. The standard spelling is свёкла, with ё, and it tells you the pronunciation and the stress.

In everyday Russian typing, many native speakers write е instead of ё, so you may see свекла, but it is still pronounced with yo, not plain e.

So for learning purposes:

• write: свёкла
• pronounce: roughly svYO-kla