В офисе начались учения, и дежурная попросила всех сохранять спокойствие.

Because в офисе means in the office, referring to location.

After в, Russian can take:

• accusative for motion toward something: в офис = into the office
• prepositional for location: в офисе = in the office

Here the sentence describes where the drills started, not movement into the office, so в офисе is correct.

Учения is one of those Russian nouns that is normally used in the plural when it means drills, training exercises, or military/emergency exercises.

So although English might say a drill or drills, Russian often uses учения as a plural-form noun for this kind of event.

That is why the verb is also plural:

• учения начались = the drills began

Because the subject is учения, which is grammatically plural.

So the verb must agree with it:

• учения начались = the drills began

Compare:

• занятие началось = the lesson began, singular
• учения начались = the drills began, plural

Начались is the past plural form of the perfective verb начаться.

The perfective aspect is used because the sentence refers to the event as a completed starting point:

• начались = started / began

If you used the imperfective начинались, it would usually suggest repeated action, background description, or a process in some context, which is not the main point here.

So начались focuses on the fact that the drills began.

Дежурная means something like the female attendant, the woman on duty, or the duty officer/staff member, depending on context.

It is feminine because the sentence refers to a woman. Russian often marks gender clearly in nouns referring to people:

• masculine: дежурный
• feminine: дежурная

That is also why the past-tense verb is feminine:

• попросила, not попросил

So:

• дежурная попросила = the woman on duty asked

Попросила is the perfective form of просить and usually means asked in the sense of making one complete request.

That fits this sentence well: she made a specific request at that moment.

Compare:

• попросила = asked once, as a completed action
• просила = was asking / asked repeatedly / used to ask, depending on context

Here the idea is a single request made after the drills started, so попросила is the natural choice.

Всех is the accusative form of все and means everyone here.

In the construction попросить кого-то сделать что-то:

• кого-то is the person being asked
• сделать что-то is what they are asked to do

So:

• попросила всех сохранять спокойствие = asked everyone to remain calm

Why всех and not все? Because it functions as the direct object of попросила.

Сохранять спокойствие literally means to preserve calm or to remain calm. It is a very common expression in formal announcements, emergencies, and public instructions.

It sounds appropriate in a drill or emergency setting.

Compare:

• сохранять спокойствие = remain calm / keep calm
• успокоиться = calm down

Успокоиться suggests that people are already agitated and need to become calm.
Сохранять спокойствие suggests maintaining calm from the start, which is more typical in official speech.

After попросить, Russian often uses an infinitive to express what someone is asked to do. Here сохранять is imperfective because it emphasizes an ongoing state or continued behavior:

• сохранять спокойствие = to remain calm / to keep calm

If a perfective verb were used, it would sound more like achieving a one-time result. But calmness here is something people should maintain over a period of time, so the imperfective is the better fit.

Спокойствие is in the accusative case.

In the phrase сохранять спокойствие, the noun is the direct object of the verb сохранять:

• сохранять что? → спокойствие

For neuter inanimate nouns like спокойствие, the accusative looks the same as the nominative, so the form does not change.

Yes, the word order is natural, but Russian word order is flexible.

The given sentence:

• В офисе начались учения, и дежурная попросила всех сохранять спокойствие.

This sounds neutral and smooth:

1. location first: В офисе
2. event: начались учения
3. next action: и дежурная попросила...

You could rearrange parts for emphasis, for example:

• Учения начались в офисе, и дежурная попросила всех сохранять спокойствие.

That version puts slightly more focus on учения first. Both are grammatical, but the original is very natural if the setting, in the office, is important information to establish right away.

Yes. Учения often refers to drills, especially emergency, safety, military, or evacuation drills. It can sound more official than a casual practice session.

In an office context, it would most naturally mean something like:

• emergency drills
• evacuation drills
• training exercises

That fits well with the second part of the sentence, where the woman on duty asks everyone to remain calm.