В салат я добавил кукурузу и горох, а сестра попросила ещё немного уксуса.

Because в can take either the accusative or the prepositional case, depending on the meaning.

• в салат = into the salad / to the salad → direction or result, so accusative
• в салате = in the salad → location, so prepositional

Here the idea is that something was added to the salad, so Russian treats it like movement/change into something: в салат.

Russian word order is much more flexible than English word order. The sentence starts with В салат to set the scene or highlight where the ingredients were added.

So:

• Я добавил кукурузу и горох в салат = neutral, straightforward
• В салат я добавил кукурузу и горох = puts extra focus on the salad

This kind of fronting is very common in Russian. It does not usually change the basic meaning, but it changes what sounds more prominent or topical.

Добавил is the past tense masculine singular form of добавить.

That means the speaker is understood to be male.

Compare:

• я добавил = I added (male speaker)
• я добавила = I added (female speaker)

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

Because кукуруза is the direct object of добавил, so it has to be in the accusative case.

For a feminine noun ending in -а, the accusative singular usually changes to -у:

• кукуруза → nominative
• кукурузу → accusative

So добавил кукурузу means added corn.

Because горох is a masculine inanimate noun, and for most masculine inanimate nouns, the accusative singular is the same as the nominative singular.

So:

• горох = nominative
• горох = accusative

That is why you see:

• добавил кукурузу и горох

One object changes form, the other does not, because they belong to different noun types.

А often connects two clauses that are related but contrasted in some way.

Here the idea is something like:

• I added corn and peas to the salad, whereas my sister asked for a little more vinegar.

It is not a strong contradiction, so но would sound too much like but in a more oppositional sense.

And и would simply mean and, without that mild contrast between my action and my sister’s action.

So а is very natural here.

Russian often leaves out possessive words like мой / моя / моё / мои when the relationship is obvious from context.

So сестра here naturally means my sister if the speaker is talking about their own family member and there is no need to specify.

Russian uses possessives less often than English does in these situations.

Попросила is the past tense feminine singular form of попросить.

It tells you two things:

1. the subject is female
2. the action is viewed as a completed/request event

So:

• сестра попросила = the sister asked / my sister asked
• if the subject were male: брат попросил

Also, попросить is perfective, so it refers to a single completed request rather than an ongoing process.

Ещё here means more or some more.

So:

• немного уксуса = a little vinegar
• ещё немного уксуса = a little more vinegar

This is a very common use of ещё. Depending on context, ещё can also mean still or yet, but here it clearly means more/additional.

Because after words like немного, Russian normally uses the genitive case.

So:

• уксус = nominative
• уксуса = genitive

This happens especially with quantities and amounts:

• много воды = a lot of water
• мало времени = little time
• немного сахара = a little sugar
• немного уксуса = a little vinegar

This is very important with uncountable substances like vinegar, sugar, milk, etc.

Here немного functions as a quantity word, roughly like a little.

It is not describing the verb; it is describing how much vinegar was requested. So it behaves more like a quantifier than a simple adverb.

In practice, the key thing for learners is this:

• after немного, the following noun usually goes into the genitive

So you can think of немного уксуса as a fixed quantity pattern.

Because а is joining two separate clauses, each with its own verb:

1. В салат я добавил кукурузу и горох
2. сестра попросила ещё немного уксуса

In Russian, when coordinating clauses like this, a comma is normally required before а.

Yes, often it could be omitted if the context already makes the subject clear:

• В салат добавил кукурузу и горох...

However, keeping я can make the contrast with сестра clearer:

• I added..., and my sister asked...

So in this sentence, я helps balance the two parts of the sentence and makes the contrast more natural.

Because добавил is perfective, and it presents the action as a single completed event: the speaker added the ingredients.

Compare:

• добавил = added, completed action
• добавлял = was adding / used to add / added repeatedly, depending on context

In this sentence, the speaker is simply reporting what was added, so добавил is the natural choice.

In a sentence like this, горох usually means peas as a food ingredient in a general sense. In real-life context, especially in salad, many speakers would understand it as something like canned peas unless the situation suggests otherwise.

Russian often uses a singular-looking noun for something English might express as a plural food item. The exact practical meaning comes from context.