Из‑за маленького недоразумения коллеги сначала молчали, а потом спокойно поговорили.

Here из-за means because of.

It is a fixed preposition written with a hyphen: из-за. Russian also uses it in a literal spatial sense, meaning from behind, but in this sentence it clearly has the causal meaning because of.

A very important grammar point: из-за normally takes the genitive case, which is why you get маленького недоразумения.

Because из-за requires the genitive case.

The base forms are:

• маленькое = small, little
• недоразумение = misunderstanding

After из-за, they become:

• маленького
• недоразумения

So:

• из-за недоразумения = because of a misunderstanding
• из-за маленького недоразумения = because of a small/minor misunderstanding

The adjective маленького matches the noun недоразумения in case, number, and gender.

Both are possible.

• маленький literally means small
• небольшой often means small/minor/not very big

With abstract things like недоразумение, Russian often uses either one.
маленькое недоразумение sounds like a little misunderstanding or a minor misunderstanding.

So this is natural Russian; it just has a slightly conversational, human tone.

It can mean either, depending on context:

• коллега = a colleague
• коллеги = colleagues / of a colleague / to colleagues, depending on case and context

In this sentence, коллеги is clearly plural nominative, meaning colleagues, because the verbs are plural:

• молчали = were silent / kept silent
• поговорили = talked

So the subject is the colleagues.

Russian has no articles like the or a/an.

So Russian often leaves it to context whether something is:

• a misunderstanding
• the misunderstanding
• colleagues
• the colleagues

That is completely normal. English needs articles; Russian does not.

They mark the sequence of events:

• сначала = at first / first
• потом = then / afterwards

So the structure is:

• сначала молчали = at first they were silent
• а потом спокойно поговорили = and then they talked calmly

This is a very common way to describe events in order.

Both а and и can connect parts of a sentence, but they are not the same.

Here а works well because it marks a contrast or change of situation:

• first they were silent,
• but/and then they talked calmly.

So а потом highlights the shift from one state to another.

If you used и потом, it would sound more like simple addition.
With а потом, the sentence feels more natural because silence and talking are contrasting stages.

молчали is the past tense plural of молчать, which means:

• to be silent
• to keep silent
• not to speak

So коллеги сначала молчали means the colleagues were not speaking at first.

This verb is imperfective, which fits well because it describes an ongoing state or situation in the past.

This is a classic Russian aspect question.

• говорили = imperfective, were talking / used to talk / talked with focus on process
• поговорили = perfective, had a talk / talked for a while, with focus on the action as a completed event

In this sentence, поговорили suggests that after the silence, they did in fact have a conversation, and that event is seen as completed.

So the sentence presents two stages:

1. they were silent
2. then they had a calm talk

That is why поговорили works very naturally here.

In many verbs of speaking, по- can suggest doing something for a while or having a bit of an activity, often as a complete event.

So поговорить often means:

• to have a talk
• to talk for a while
• to speak and finish speaking

Here it does not necessarily mean the talk was short, but it does present it as a single completed event.

Because спокойно is an adverb, and it modifies the verb поговорили.

• спокойный = calm (adjective, masculine)
• спокойная = calm (adjective, feminine)
• спокойное = calm (adjective, neuter)
• спокойно = calmly (adverb)

So:

• спокойный коллега = a calm colleague
• спокойно поговорили = talked calmly

English often uses calm both as an adjective and in expressions like remain calm, but here Russian needs the adverb form.

Russian often omits subject pronouns when the subject is already clear from context.

Since коллеги is already the subject, there is no need to add они.

So:

• коллеги сначала молчали, а потом спокойно поговорили
  is more natural than
• коллеги сначала молчали, а потом они спокойно поговорили

Adding они is possible, but it would usually add emphasis or feel unnecessary here.

Yes, Russian word order is flexible, although the original sentence is very natural.

For example, you could also say:

• Сначала коллеги молчали, а потом спокойно поговорили.
• Коллеги из-за маленького недоразумения сначала молчали, а потом спокойно поговорили.

The original version puts из-за маленького недоразумения first, which sets up the reason right away.

So the sentence structure does this:

1. gives the cause
2. names the subject
3. shows the sequence of actions

That makes it smooth and easy to follow.

Because а joins two coordinated parts of the sentence, and Russian normally puts a comma before it.

The sentence has two linked parts:

• коллеги сначала молчали
• а потом спокойно поговорили

So the comma is standard punctuation before а.

A few useful stress points are:

• из-за́
• ма́ленького
• недоразуме́ния
• колле́ги
• сначала́
• молча́ли
• пото́м
• споко́йно
• поговори́ли

A learner should especially notice недоразуме́ния, because it is long and the stress is not where an English speaker might guess.