Утром я сделал бутерброд с авокадо и взял с собой мандарин.

Утром is a common adverbial form meaning in the morning.

It comes from the noun утро (morning), but in this use Russian puts it in the instrumental form: утром.

Compare:

• утро = morning
• утром = in the morning

This is a very common pattern:

• днём = during the day
• вечером = in the evening
• ночью = at night

So Утром я сделал... means In the morning, I made...

This is about verb aspect.

• делать = imperfective, focusing on the process, repetition, or ongoing action
• сделать = perfective, focusing on the completed result

In this sentence, the speaker means they finished making the sandwich, so сделал is natural.

Compare:

• Я делал бутерброд. = I was making a sandwich / I used to make a sandwich
• Я сделал бутерброд. = I made a sandwich, and it was completed

Because the sentence describes completed morning actions, perfective verbs fit well:

• сделал
• взял

Russian often omits a repeated subject when it is already clear.

So:

• Утром я сделал бутерброд с авокадо и взял с собой мандарин.

literally is:

• In the morning I made an avocado sandwich and took a mandarin with me.

The second я is unnecessary because the subject is obviously the same person.

You could say:

• ...и я взял с собой мандарин

but it sounds more explicit or slightly heavier. The version without the second я is more natural here.

Because бутерброд is the direct object of сделал, and here it is an inanimate masculine noun.

For inanimate masculine nouns in the singular:

• nominative = accusative

So:

• nominative: бутерброд
• accusative: бутерброд

That is why the form does not change.

Compare with an animate masculine noun:

• я вижу брата = I see my brother

But with an inanimate noun:

• я вижу стол = I see a table

The preposition с here means with.

So:

• бутерброд с авокадо = a sandwich with avocado

After с in this meaning, Russian normally uses the instrumental case.

That is why many nouns change after с:

• с сыром = with cheese
• с маслом = with butter
• с курицей = with chicken

But авокадо is one of those borrowed nouns that usually does not change across cases in modern Russian. So even though instrumental is required grammatically, the word itself stays авокадо.

Because авокадо is an indeclinable noun in Russian.

That means it usually keeps the same form in all cases:

• авокадо
• нет авокадо
• с авокадо
• люблю авокадо

Many borrowed words in Russian behave this way.

So in бутерброд с авокадо, the case is still determined by the grammar, but the word itself does not visibly change.

Not always exactly.

Бутерброд often means a piece of bread with something on it, or a simple sandwich. In everyday use, it can overlap with English sandwich, but it may also suggest something more open-faced than an English sandwich.

In modern speech, Russians may also use:

• сэндвич = sandwich, often a more specifically Western-style or closed sandwich

So in this sentence, бутерброд с авокадо is naturally translated as an avocado sandwich, even though the Russian word does not always match English sandwich perfectly in every context.

Again, this is a question of aspect.

• брать = imperfective, to take, to be taking, to take repeatedly
• взять = perfective, to take successfully, as a completed action

Here the speaker means a single completed action:

• they took a mandarin with them

So взял is the normal choice.

Compare:

• Я брал с собой мандарин каждый день. = I used to take a mandarin with me every day
• Я взял с собой мандарин. = I took a mandarin with me

С собой means with oneself / along with oneself.

So:

• взять с собой = to take with you
• нести с собой = to carry with you

This is a very common Russian expression.

Without с собой, взять мандарин just means to take a mandarin.
With с собой, it specifically means to take it along somewhere.

So:

• взял с собой мандарин = took a mandarin along / took a mandarin with him

Because мандарин is also a direct object, and it is inanimate masculine singular.

For inanimate masculine singular nouns:

• nominative = accusative

So:

• nominative: мандарин
• accusative: мандарин

That is why the form stays the same.

Be careful: мандарин can also mean Mandarin in some contexts, but here it clearly means the fruit.

Yes. Russian мандарин can mean:

• a mandarin/tangerine fruit
• in some contexts, a Mandarin official or something related to Mandarin Chinese

But in everyday life, especially in a sentence about food, мандарин is understood as the fruit.

So in this sentence there is no real ambiguity.

Yes, Russian word order is flexible.

The given sentence is natural and neutral:

• Утром я сделал бутерброд с авокадо и взял с собой мандарин.

But other orders are possible depending on emphasis:

• Я утром сделал бутерброд с авокадо и взял с собой мандарин.
• Бутерброд с авокадо я сделал утром и взял с собой мандарин.

The first version sounds the most straightforward. Putting утром first helps set the time frame right away.

So the word order here is natural, but not the only grammatically correct one.

Normally, утром is understood to apply to the whole sequence:

• in the morning, I made a sandwich and took a mandarin with me

So it naturally covers both сделал and взял, unless context suggests otherwise.

Russian often places a time expression at the beginning of the sentence to frame everything that follows.

No, not with this meaning.

• утром = in the morning
• на утро usually means something like for the morning or appears in different constructions, often with a different sense

For example:

• Я оставил это на утро. = I left it for the morning

But in your sentence, where the meaning is in the morning, you need утром.

Because these are past tense singular masculine forms.

In Russian past tense, the verb agrees with the subject in gender and number.

For я, the form depends on whether the speaker is male or female:

• male speaker: я сделал, я взял
• female speaker: я сделала, я взяла

So the sentence as written suggests that the speaker is male.
If the speaker were female, it would be:

• Утром я сделала бутерброд с авокадо и взяла с собой мандарин.