bogoseoreul da ilggo naseo dapjanghalgeyo.

A natural breakdown is:

• 보고서 = report
• -를 = object marker
• 다 = all, completely
• 읽고 나서 = after reading
• 답장할게요 = I’ll reply / I’ll send a reply

So the structure is basically:

[report + object marker] + [completely read + after] + [reply + -ㄹ게요]

It literally feels like:

After reading the report completely, I’ll reply.

Because 보고서 is the thing being read, so it is the direct object of 읽다 (to read).

• 보고서를 읽다 = to read the report

The particle -를 / -을 marks the object of the verb.

By contrast, -가 / -이 usually marks the subject. So 보고서가 would sound like the report is the subject of something, which is not what is happening here.

Here, 다 means all or completely.

So:

• 보고서를 읽고 나서 = after reading the report
• 보고서를 다 읽고 나서 = after reading the whole report / after finishing reading the report

It emphasizes completion. In English, we often translate it naturally as after I’ve finished reading the report.

-고 나서 means after doing X, then... It strongly emphasizes that one action happens first, and the next action happens after that is completed.

So:

• 읽고 나서 답장할게요 = I’ll reply after reading it

If you used just -고, the sentence could still connect two actions, but -고 나서 more clearly highlights the sequence:

1. read the report first
2. reply afterward

For learners, a good shortcut is:

• -고 = and / then
• -고 나서 = after doing

They are very similar in meaning.

• 읽고 나서 = after reading
• 읽은 후에 = after reading / after having read

Both are correct. The difference is mostly style and tone:

• -고 나서 is very common in everyday speech
• -은 후에 can sound a little more formal or written

So 보고서를 다 읽고 나서 답장할게요 sounds very natural in conversation.

답장할게요 comes from 답장하다 (to reply, to send a reply) plus -ㄹ게요 / -을게요.

This form is not just plain future tense. It often carries a nuance like:

• I’ll do it
• I’ll do that for now
• I intend to do it
• I’m telling you my decision/promise

So 답장할게요 feels like:

I’ll reply (to you).

It is often used when the speaker is making a decision in relation to the listener.

These are similar, but the nuance is different.

• 답장할게요
  = I’ll reply.
  Very natural in conversation; often sounds like a promise or immediate intention directed toward the listener.

• 답장하겠어요
  = I will reply.
  More formal, and can sound a bit more deliberate or stiff in everyday conversation.

• 답장할 거예요
  = I’m going to reply / I will reply.
  A more neutral future statement.

So in this sentence, 답장할게요 is a very natural choice if you are telling someone directly, I’ll reply after I finish reading the report.

Korean often leaves out subjects and objects when they are obvious from context.

So 보고서를 다 읽고 나서 답장할게요 naturally implies:

• I will reply
• probably reply to you

But Korean usually does not need to state those explicitly if the situation is clear.

This is very common and very natural.

Yes. It is in a polite speech level because it ends in -요:

• 답장할게요

This is polite and suitable for many everyday situations.

However, it is not the highest or most formal style. In a very formal business email, someone might choose something like:

• 보고서를 다 읽고 나서 답장드리겠습니다.

That sounds more formal and business-like.

So the original sentence is polite, natural, and conversational.

답장하다 specifically means to send a reply, especially in contexts like messages, emails, or letters.

• 답장하다 = to reply in writing / to send a response

답하다 means to answer, which is broader. It can be used for answering a question, a call, or a prompt.

So if the situation is replying to an email, message, or written communication, 답장하다 is a very natural choice.

Yes. -고 나서 mainly tells you the order:

1. finish reading the report
2. reply

It does not always mean the second action happens instantly. It just means the reply will come after the reading is done.

So depending on context, it can sound like:

• I’ll reply after I read the report
• I’ll reply once I’ve finished reading the report

Yes, absolutely.

• 보고서를 읽고 나서 답장할게요 = I’ll reply after reading the report
• 보고서를 다 읽고 나서 답장할게요 = I’ll reply after reading the whole report / after finishing the report

Without 다, the sentence is still correct.
With 다, the sentence more clearly emphasizes that the report will be read completely before replying.

Because 답장하다 is a 하다-verb.

Many Korean nouns combine with 하다 to form verbs:

• 답장 = reply
• 답장하다 = to reply

When conjugating it, you work with 하다:

• dictionary form: 답장하다
• future/intention with -ㄹ게요: 답장할게요

So 답장 + 할게요 is just the regular conjugation of the verb 답장하다.