Сначала нас попросили входить поодиночке, а уже потом мы смогли спокойно поговорить.

Because нас is the object, not the subject.

• мы = we as the subject
• нас = us in the accusative/genitive form

In this sentence, the idea is someone asked us, so us is being acted on:

• нас попросили = they asked us

If you said мы попросили, it would mean we asked.

Попросили is past tense plural because the subject is an unstated they.

Russian often leaves out the subject when it is unknown, obvious, or unimportant. So:

• нас попросили literally means they asked us
• but in natural English, it may simply be we were asked

This is a very common Russian pattern:

• Меня пригласили. = I was invited.
• Нас попросили подождать. = We were asked to wait.

So the plural verb does not agree with нас grammatically as an object; it reflects the omitted subject they.

This is an aspect question.

• входить = imperfective
• войти = perfective

After попросить, both aspects can be possible, but they give slightly different shades of meaning.

Here, входить suggests:

the action as a process or general instruction:

• входить поодиночке = to enter one by one, to go in individually

This sounds like a rule or procedure.

If you said войти поодиночке:

it would sound more like asking for the action to be completed as a single whole event.

In many contexts, both are possible, but входить fits very naturally when the speaker is talking about how people were supposed to enter, especially one after another.

Поодиночке is an adverb meaning:

• one by one
• individually
• separately

So входить поодиночке means entering not as a group, but each person separately.

You can compare:

• вместе = together
• поодиночке = one at a time / alone, individually

It is a fixed adverb, so you do not need to change its ending.

Сначала means at first or first.

It sets up the first stage of the sequence:

• Сначала нас попросили входить поодиночке = At first, we were asked to go in one by one

Then the sentence contrasts that with what happened later:

• а уже потом... = and only afterwards...

So сначала helps organize the timeline.

Потом means then / afterwards, but уже потом adds extra emphasis.

Here уже gives the sense of:

• only then
• not until afterwards
• after that point

So:

• а потом мы смогли поговорить = and then we were able to talk
• а уже потом мы смогли поговорить = and only afterwards were we able to talk

It highlights that the conversation happened later, not immediately.

А often marks contrast or a shift from one stage to another, while и is a more neutral and.

Here the sentence contrasts two situations:

1. first, there was a restriction: we were asked to enter one by one
2. later, the situation changed: we were able to talk calmly

So а works well because it signals that transition.

It does not have to be a strong opposition like but; often it is just a contrast in flow or circumstance.

Because смогли adds the idea of being able to, managing to, or having the opportunity to.

• мы поговорили = we talked / had a talk
• мы смогли поговорить = we were able to talk / managed to talk

In this sentence, that matters because the earlier situation seems to have prevented or delayed the conversation. So смогли shows that only later did they finally get the chance.

Again, this is aspect.

• говорить = imperfective
• поговорить = perfective

Поговорить usually means to talk for a while, to have a conversation, seen as one complete event.

After смочь, the perfective is often very natural when you mean successfully carrying out a whole action:

• смогли поговорить = were able to have a talk

If you used смогли говорить, it would sound more like were able to speak in a general sense, focusing on the activity rather than a completed conversation.

So поговорить is the better choice here.

Спокойно literally means calmly, but in context it often means something like:

• without stress
• without being rushed
• in peace
• properly

So спокойно поговорить is not just to talk calmly in an emotional sense. It often means to have a chance to talk properly, without interruption or pressure.

That is a very common Russian use of спокойно.

Russian word order is flexible, and this order is chosen for emphasis and natural flow.

The sentence puts time expressions first:

• Сначала...
• а уже потом...

This makes the timeline very clear.

Then comes:

• мы смогли спокойно поговорить

That is a natural, neutral continuation.

You could rearrange parts of the sentence, but the given order sounds smooth and emphasizes the sequence of events. Russian often moves adverbs and time words earlier in the sentence for emphasis.

Grammatically it is from попросить, which usually means to ask or to request.

In context, though, English may sometimes translate it more strongly:

• we were asked to enter one by one
• we were told to enter one by one

The Russian verb itself is not as forceful as something like приказали (ordered) or велели (commanded), but depending on the situation, English may choose told if the request was effectively an instruction.

So the core meaning is still asked/requested.

Because а is linking two clauses:

1. Сначала нас попросили входить поодиночке
2. а уже потом мы смогли спокойно поговорить

In Russian, coordinating conjunctions like а, но, and often и connect clauses with a comma.

So the comma is standard punctuation here.