Если нет времени готовить, я беру йогурт, сырник и персик.

Because after нет Russian normally uses the genitive case.

• время = nominative
• времени = genitive

So нет времени literally means there is no time. This is a very common pattern:

• нет денег = there is no money
• нет воды = there is no water
• нет возможности = there is no possibility

So in this sentence, Если нет времени... means If there is no time...

Because времени готовить means time to cook.

After nouns like время, Russian often uses an infinitive to express what there is or is not time for:

• У меня нет времени читать. = I don’t have time to read.
• Есть время отдохнуть. = There is time to rest.

So нет времени готовить is a natural way to say there’s no time to cook.

Russian often prefers an impersonal structure here.

Instead of explicitly saying I don’t have time, it says there is no time:

• У меня нет времени готовить = I don’t have time to cook
• Нет времени готовить = There’s no time to cook / If there’s no time to cook

In this sentence, the subject is understood from the second clause (я беру...), so Russian does not need to repeat у меня.

Because Если нет времени готовить is a subordinate clause introduced by если (if), and Russian normally separates that kind of clause with a comma.

So:

• Если нет времени готовить, я беру...

This is standard punctuation in Russian, even when the subordinate clause comes first.

Беру is the present tense of an imperfective verb, and here it usually expresses a habitual or regular action:

• Если нет времени готовить, я беру йогурт, сырник и персик. = When/If I don’t have time to cook, I take/get yogurt, a syrnik, and a peach.

It sounds like something the speaker typically does.

If you said я возьму, that would sound more like I will take in a specific future situation.

So:

• беру = I take / I usually take
• возьму = I’ll take

They are in the accusative case, because they are the direct objects of беру.

However, for inanimate masculine singular nouns, the accusative looks the same as the nominative. So:

• йогурт → accusative йогурт
• сырник → accusative сырник
• персик → accusative персик

That is why they look unchanged.

Compare with a feminine noun:

• я беру книгу = I take a book

There, the accusative form is visibly different.

Because the sentence is talking about individual items: a yogurt, a syrnik, and a peach.

Russian often uses singular count nouns this way when naming what someone takes/eats/buys:

• я беру яблоко = I take an apple
• он купил банан = he bought a banana

Of course, plural is also possible if the meaning changes:

• я беру персики = I take peaches
• я беру сырники = I take syrniki

But in your sentence, the speaker means one of each.

Сырник is a traditional food made from творог (farmer’s cheese / curd cheese), usually fried like a small pancake.

A learner may notice that the word looks related to сыр (cheese), but in modern usage сырник specifically means this dish, not just any cheese item.

Plural:

• сырник = one syrnik
• сырники = syrniki

Yes, very often.

Russian often drops subject pronouns when the verb already makes the person clear. So both are possible:

• Если нет времени готовить, я беру йогурт, сырник и персик.
• Если нет времени готовить, беру йогурт, сырник и персик.

The version with я is slightly more explicit and can add a bit of emphasis or clarity, but it is not required.

Because Russian has no articles.

So a noun like йогурт can mean:

• a yogurt
• the yogurt

The exact meaning depends on context.

In this sentence, English would naturally translate the list as a yogurt, a syrnik, and a peach, but Russian does not need separate words for that.

Yes. Russian word order is fairly flexible, though each version can sound slightly different in emphasis.

The given sentence is neutral and natural:

• Если нет времени готовить, я беру йогурт, сырник и персик.

But you could also hear:

• Если нет времени готовить, беру йогурт, сырник и персик.
• Я, если нет времени готовить, беру йогурт, сырник и персик.

The basic meaning stays the same, but the original version is a very standard, straightforward way to say it.