Если завтра мне снова будет некогда готовить, я куплю готовые блины и кефир в магазине.

Because Russian very often uses an impersonal construction here:

• кому?
  • будет некогда
    • infinitive

So:

• мне будет некогда готовить = I won’t have time to cook / it will be inconvenient for me to cook because I’ll have no time

The word некогда is a fixed word meaning there is no time or one has no time. This is much more natural in Russian than a literal to have time expression in many everyday contexts.

So the sentence structure is not really I will be... but more like:

• To me, it will be no-time to cook
  which idiomatically means
• I won’t have time to cook

Because in this impersonal pattern, the person experiencing the situation is put in the dative.

Compare:

• Мне некогда. = I have no time.
• Тебе некогда. = You have no time.
• Нам некогда. = We have no time.

So мне does not mean me in the direct-object sense here. It marks the person affected by the situation.

This is a very common Russian pattern with words like:

• мне нужно = I need
• мне можно = I may / I’m allowed
• мне трудно = it is difficult for me
• мне некогда = I have no time

Because некогда is followed by an infinitive to show what there is no time to do.

So:

• мне некогда готовить = I have no time to cook
• мне некогда читать = I have no time to read
• мне некогда звонить = I have no time to call

The infinitive names the action in a general way. In this sentence, it answers the question:

• No time to do what?
• готовить

This is a very important difference between English and Russian.

In Russian, when you talk about a real future condition, you normally use the future tense in both parts:

• Если завтра мне снова будет некогда готовить, я куплю...

Literally:

• If tomorrow I again will-have-no-time to cook, I will buy...

That is normal Russian.

English usually avoids will after if in this kind of sentence, but Russian does not. So this is one of those places where you should not copy English grammar.

More examples:

• Если завтра будет дождь, мы останемся дома.
  = If it rains tomorrow, we’ll stay home.

• Если он придёт, я поговорю с ним.
  = If he comes, I’ll talk to him.

Because куплю is the perfective future of купить, and it fits the meaning of a single completed action:

• я куплю = I will buy

The speaker means one concrete action in the future: if there’s no time, they will go and buy those things.

If you said буду покупать, that would sound more like:

• a process,
• repeated buying,
• or focus on the activity rather than the result.

Here the result matters: I’ll buy ready-made pancakes and kefir. So куплю is the natural choice.

Because the two verbs express different kinds of actions.

готовить — imperfective

Here it means to cook in a general sense. The sentence is about whether there is time for the activity of cooking at all.

• некогда готовить = no time to cook

The focus is not on finishing the cooking; it is on the activity.

куплю — perfective

This is a specific one-time future action with a clear result:

• I’ll buy them

So Russian uses:

• imperfective for the general activity: готовить
• perfective for the one completed future action: куплю

Снова means again.

So:

• завтра мне снова будет некогда готовить
  = tomorrow I again won’t have time to cook

It suggests this is not the first time this has happened. Maybe the speaker has already been busy before, and tomorrow the same problem may happen again.

In this sentence, снова modifies the whole situation будет некогда.

Готовые блины means ready-made pancakes.

Agreement

The adjective готовые agrees with блины in:

• number: plural
• gender: not relevant in plural
• case: accusative plural here

Why does it look like nominative plural?

Because блины are inanimate, and in Russian the accusative plural of inanimate nouns is the same as the nominative plural.

So:

• nominative: готовые блины
• accusative: куплю готовые блины

That is why the form does not change.

Because that is simply how those foods are naturally referred to here.

• блины are countable items, so plural makes sense: pancakes / crepes
• кефир is usually treated as an uncountable product, like milk or yogurt in English

So the speaker is buying:

• some ready-made pancakes
• some kefir

Russian often uses singular mass nouns this way:

• купить молоко = buy milk
• купить хлеб = buy bread
• купить кефир = buy kefir

Russian uses в магазине to mean in / at the store.

• в
  • prepositional case = location inside or at a place
• магазине is the prepositional singular form of магазин

So:

• в магазине = in the store / at the store

You could omit it if the location is obvious:

• я куплю готовые блины и кефир

But adding в магазине makes it explicit that the speaker will buy them at a store, not make them, order them, or get them somewhere else.

Yes, you could. Russian word order is relatively flexible.

These are all possible, with slightly different emphasis:

• Если завтра мне снова будет некогда готовить, я куплю...
• Если мне завтра снова будет некогда готовить, я куплю...
• Если снова завтра мне будет некогда готовить, я куплю...
  though this last one is less neutral and more marked

The original version sounds natural and neutral. Putting завтра near the beginning highlights the time frame early.

So the word order is not random, but it is more flexible than in English.

Because the sentence has two clauses:

1. Если завтра мне снова будет некогда готовить
   = the if-clause (subordinate clause)

2. я куплю готовые блины и кефир в магазине
   = the main clause

In Russian, a subordinate clause introduced by если is separated by a comma.

So the comma is required:

• Если ..., я ...

Because this is an impersonal sentence.

There is no subject like я in the first clause. Russian does not say:

• я буду некогда ❌

Instead, it uses the pattern:

• мне будет некогда

This construction describes a state or situation affecting someone, rather than an action performed by a grammatical subject.

So in the first clause:

• мне = the person affected
• будет = future of быть
• некогда = no time
• готовить = what there is no time to do

That whole clause naturally has no nominative subject.