По утрам я часто ем хлопья с йогуртом, когда мне некогда готовить.

По утрам means in the mornings or every morning / on mornings in general. It emphasizes a repeated, habitual time.

• По утрам я часто ем хлопья... = In the mornings, I often eat cereal...
• Утром can also mean in the morning, but it is less explicitly repetitive by itself.

So here по утрам is a very natural choice because the sentence describes a routine.

Because the preposition по often takes the dative case in expressions of repeated time.

• утро = nominative singular
• утрам = dative plural

So:

• по утрам = in the mornings
• literally something like along mornings / on mornings

This is a common pattern in Russian:

• по вечерам = in the evenings
• по выходным = on weekends
• по понедельникам = on Mondays

Yes, я could be omitted.

Russian verbs usually show the subject clearly, and ем already means I eat, so:

• По утрам я часто ем хлопья...
• По утрам часто ем хлопья...

Both are possible.

Including я makes the sentence a little more explicit and neutral. Omitting it can sound slightly more conversational, especially if the subject is already obvious from context.

Because ем is the first-person singular form of the verb есть (to eat).

The forms are:

• я ем = I eat
• ты ешь = you eat
• он/она ест = he/she eats
• мы едим = we eat
• вы едите = you eat
• они едят = they eat

So есть is the dictionary form, and ем is the form that matches я.

Хлопья means flakes or cereal flakes, and in food contexts it often refers to things like breakfast cereal, oat flakes, cornflakes, etc.

It is usually used in the plural in this meaning:

• есть хлопья = to eat cereal / flakes
• овсяные хлопья = oat flakes
• кукурузные хлопья = cornflakes

So although English often uses singular cereal, Russian commonly uses a plural noun here.

Also, in this sentence хлопья is the direct object of ем, and because it is inanimate, the accusative plural looks the same as the nominative plural.

Because after с meaning with, Russian normally uses the instrumental case.

• йогурт = nominative
• йогуртом = instrumental

So:

• с йогуртом = with yogurt

This is a very common pattern:

• с молоком = with milk
• с сахаром = with sugar
• с фруктами = with fruit

Very literally, мне некогда готовить is something like:

• to me there is no time to cook

But in natural English it means:

• when I don’t have time to cook
• when I’m too busy to cook

This is a very common Russian structure. Russian often uses the dative case for the person experiencing a state:

• мне холодно = I am cold
• мне скучно = I am bored
• мне некогда = I have no time

So мне is not a direct translation of I here; it is part of a Russian pattern.

Because in expressions like мне некогда, the person is treated as the experiencer of the situation, and Russian commonly marks that with the dative.

So:

• я = I
• мне = to me

This same pattern appears in many impersonal expressions:

• мне нужно = I need
• мне нельзя = I’m not allowed / I must not
• мне трудно = it’s hard for me

So мне некогда готовить is structurally more like It is not-time for me to cook than I don’t have time to cook.

Yes, here it is one word: некогда.

In this sentence, некогда means:

• there is no time
• no time to...

So:

• мне некогда готовить = I don’t have time to cook

By contrast, не когда as two words would mean something different, literally not when, and would only appear in special contexts.

So in this sentence, it must be некогда as one word.

Because the sentence is talking about the general activity of cooking, not about completing one specific dish.

• готовить = to cook, be cooking, do cooking in general
• приготовить = to prepare, cook something to completion

Here the idea is:

• when I don’t have time to cook

That is a general situation, so готовить is the natural choice.

If you used приготовить, it would sound more like:

• when I don’t have time to prepare something / cook a finished dish

Possible in some contexts, but less neutral here.

Because когда мне некогда готовить is a subordinate clause.

Russian normally uses a comma to separate a main clause from a dependent clause introduced by words like:

• когда = when
• если = if
• потому что = because
• хотя = although

So the structure is:

• По утрам я часто ем хлопья с йогуртом = main clause
• когда мне некогда готовить = subordinate clause

That is why the comma is required.

It can feel like whenever in English.

Because the whole sentence describes a repeated habit, когда does not refer to just one single moment. It means something like:

• when / whenever I don’t have time to cook

This is very natural in Russian. You do not always need a separate word for whenever if the context already makes the meaning habitual.

No, Russian word order is fairly flexible, although some orders sound more neutral than others.

The original sentence is very natural and neutral:

• По утрам я часто ем хлопья с йогуртом, когда мне некогда готовить.

You could also say:

• Я часто ем по утрам хлопья с йогуртом...
• Часто по утрам я ем хлопья с йогуртом...

But changing the word order changes what feels emphasized:

• по утрам at the start highlights the time frame
• часто near the verb highlights frequency
• я can be moved or omitted depending on emphasis

So the sentence is not rigid, but the original order is a very good default.