sajangnimi da-eum dare gyeyak naeyongeul dasi hwaginhajago haesseo.

-자고 했어 is the indirect-quotation form for a suggestion.

• 확인하자 = let's check / let's confirm
• 확인하자고 했어 = (someone) said we should check / suggested checking

So the boss is not simply stating a fact. He is proposing that they check the contract details again next month.

They are similar, but the nuance is different:

• 확인하자고 했어 = said, “let’s confirm/check”
  → a suggestion including the speaker/listener group
  → like Let’s check it again

• 확인하라고 했어 = told (someone) to confirm/check
  → more like an instruction or command
  → like He told us to check it again

So in your sentence, the boss is presented as suggesting a joint action, not just ordering someone else to do it.

이/가 marks the subject, while 은/는 marks the topic.

Here, 사장님이 simply identifies the boss as the person who said it.

• 사장님이 ... 했어 = The boss said...
• 사장님은 ... 했어 could sound more like As for the boss, he said... or add contrast depending on context.

In many isolated example sentences, 이/가 is the most neutral choice for the subject.

사장 usually means something like company president / CEO / boss / owner, depending on context.

님 is an honorific suffix that shows respect. So:

• 사장 = boss/president
• 사장님 = boss/president with respect

In Korean, titles are often used instead of names, especially in workplace situations.

다음 달 means next month.

The particle 에 marks a time point or time setting, so:

• 다음 달에 = next month / in next month

In English, we often do not think of a separate marker here, but Korean commonly uses 에 with specific times.

Examples:

• 월요일에 = on Monday
• 세 시에 = at three o’clock
• 다음 달에 = next month

계약 내용 is a noun phrase meaning the contents/details of the contract.

Breakdown:

• 계약 = contract
• 내용 = content/details
• 계약 내용 = contract details / contents of the contract
• 계약 내용을 = contract details + object marker

The object marker is attached to the whole noun phrase, and the main noun is 내용, not 계약.

So 계약 내용을 확인하다 means to check the contents/details of the contract.

다시 means again.

So:

• 확인하다 = to check / confirm
• 다시 확인하다 = to check again / reconfirm

It tells you that this is not the first check. They want to go over the contract details one more time.

Yes. In 확인하자고, the subject is not explicitly stated, but it is usually understood as we.

Because -자 means let’s..., it normally includes:

• the speaker
• the listener
• possibly others in the group, depending on context

So the idea is basically: The boss said, “Let’s check the contract details again next month.”

Korean often leaves out pronouns when they are understood from context.

Because the sentence ending shows the relationship between the speaker and the listener, not necessarily the level of respect toward the person being talked about.

So:

• 했어 = casual/informal speech to the listener
• 했어요 = polite speech to the listener
• 했습니다 = formal speech to the listener

You can still refer respectfully to the boss with 사장님, even if you are speaking casually to a friend:

• 사장님이 ... 했어 = casual to your friend, but still respectful toward the boss through 님

Yes. A more honorific version would be:

사장님께서 다음 달에 계약 내용을 다시 확인하자고 하셨어요.

Changes:

• 사장님이 → 사장님께서
  (께서 is the honorific subject marker)
• 했어 → 하셨어요
  (honorific verb form + polite ending)

The original sentence is completely natural in casual conversation, but this version sounds more respectful toward the boss.

Korean word order is fairly flexible as long as the particles and overall structure remain clear.

Original: 사장님이 다음 달에 계약 내용을 다시 확인하자고 했어.

Possible variation: 사장님이 계약 내용을 다음 달에 다시 확인하자고 했어.

Both are understandable. The original order sounds very natural, with the time phrase 다음 달에 appearing early.

The verb and quotation structure usually stay near the end:

• 확인하자고 했어

That final part is important because Korean sentences typically place the main verb at the end.

Yes. 확인하다 often covers both ideas.

Depending on context, it can mean:

• check
• confirm
• verify

In this sentence, English translations like these are all reasonable:

• check the contract details again
• confirm the contract details again
• go over the contract details again

The exact best choice depends on the situation, but the Korean itself is very natural and broad.

By itself, 다음 달에 just means at some point next month. It does not mean specifically the first day or the beginning of the month.

If Korean wanted to be more specific, it could say things like:

• 다음 달 초에 = at the beginning of next month
• 다음 달 말에 = at the end of next month
• 다음 달 15일에 = on the 15th of next month

So the original sentence leaves the exact timing open.