sonnimi ogi jeone geosireul kkalkkeumhage jeongrihae nohasseoyo.

Because -기 turns a verb into a noun-like form.

• 오다 = to come
• 오기 = coming

Then that noun-like form combines with 전 / 전에, which means before.

So:

• 오기 전에 = before coming / before someone comes

This is a very common pattern:

• 먹기 전에 = before eating
• 자기 전에 = before sleeping
• 출발하기 전에 = before departing

With before, Korean normally uses verb stem + -기 전에.

So the natural form is:

• 오다 → 오기 전에

Why not the others?

• 오는 전에 is not the normal pattern here.
• 왔기 전에 would sound like before having come, which usually does not fit the intended meaning.

The idea is that the action of coming had not happened yet at the time the living room was tidied. So Korean uses 오기 전에, not a past form.

손님이 is the subject of the clause 손님이 오기 전에.

That clause means:

• before the guest(s) come

Here, 이/가 marks who is doing the coming.

So:

• 손님이 오기 전에 = before the guest(s) come
• 손님은 would add a topic or contrast nuance, which is usually not the main point here

In this sentence, the speaker is simply identifying who is coming, so 이/가 is the natural choice.

Because 거실 is the direct object of 정리하다.

• 거실 = living room
• 정리하다 = to organize / tidy up

So the speaker is tidying the living room, which makes it the object:

• 거실을 정리하다 = to tidy the living room

깔끔하게 is the adverb form of 깔끔하다.

• 깔끔하다 = to be neat / clean / tidy
• 깔끔하게 = neatly / tidily

The ending -게 often turns descriptive words into adverbs.

So:

• 깔끔한 방 = a neat room
• 방을 깔끔하게 정리하다 = to tidy the room neatly

In this sentence, 깔끔하게 describes how the speaker organized the living room.

This is one of the most important points in the sentence.

• 정리했어요 = I tidied it / organized it
• 정리해 놓았어요 = I tidied it and left it that way, usually in preparation for something

The grammar -아/어 놓다 adds the idea of:

• doing something in advance
• completing it and leaving the result in place
• being prepared for a later situation

So in this sentence, 정리해 놓았어요 suggests:

• the living room was tidied up beforehand
• it was done for the guests
• the room was left in a neat state

That nuance is stronger than just 정리했어요.

Because the tidying action had already been completed.

• 놓다 becomes 놓았어요 in past polite form
• together with 정리해, it becomes 정리해 놓았어요

This shows that the speaker is talking about something already done:

• they had already tidied the living room
• and the result remained

Even though 오기 전에 refers to a later event relative to the tidying, the main action itself is presented as completed.

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

The sentence does not explicitly say 제가 or 내가, but English often needs I:

• (제가) 손님이 오기 전에 거실을 깔끔하게 정리해 놓았어요.

This omitted subject is very normal in Korean. If the situation already makes it clear who did the tidying, there is no need to say it.

It can mean either guest or guests.

Korean nouns often do not have to show singular vs. plural unless it matters.

So:

• 손님이 오기 전에 can mean before the guest comes
• or before the guests come

If the speaker wants to make plural explicit, they could say:

• 손님들이 오기 전에

But in many everyday sentences, plain 손님 is enough.

Yes. In everyday conversation, it is often shortened to 정리해 뒀어요.

So these are closely related:

• 정리해 놓았어요 = full form
• 정리해 뒀어요 = common spoken contraction

Both mean essentially the same thing, but 정리해 뒀어요 sounds more natural in casual everyday speech.

Not necessarily.

It means the tidying happened before the guests’ coming, but the sentence itself does not always guarantee whether they have already arrived by the time of speaking. That depends on context.

What the sentence clearly tells you is:

• the living room was tidied in advance
• the reason or timing was related to the guests coming

So depending on context, it could mean:

• I tidied the living room before the guests arrived
• or I had the living room tidied up before the guests came

The important grammatical idea is the before relationship, not necessarily the full timeline beyond that.

It sounds natural, polite, and a little careful or considerate.

The sentence suggests:

• the speaker was preparing for guests
• they made the living room neat beforehand
• they were being thoughtful or organized

That feeling comes especially from:

• 깔끔하게 = neatly
• 정리해 놓았어요 = tidied up in advance and left it ready

So the sentence does not just describe cleaning; it also conveys preparation and consideration for visitors.