bangeul cheongsohaeseo ije kkaekkeushaeyo.

방 = room.
을 is the object particle, showing that 방 is what the verb 청소하다 (to clean) is acting on: (I) clean the room.
If you used 방이, it would mark 방 as the subject, which doesn’t fit well with 청소하다 in this sentence.

Korean often omits the subject when it’s clear from context.
방을 청소해서 이제 깨끗해요 naturally implies something like (제가/우리가) 방을 청소해서… or sometimes just a general statement about the situation.

They’re different:

• 청소했어요 = I cleaned (it). (just a finished past action)
• 청소해서 = because/so/after cleaning (it), … (connects to the next clause)

-아서/어서 links two clauses and commonly expresses: 1) cause → result: I cleaned it, so now it’s clean.
2) sometimes sequence: I cleaned it and then… (context decides)

Here it’s mainly cause/result.

Yes, -아서/어서 can be read as either so/because or and then, but in this sentence the natural interpretation is cause → result because 깨끗해요 describes the resulting state.

Because the sentence is about the current state now:

• 이제 깨끗해요 = Now it’s clean.

깨끗했어요 would mean it was clean (at some past time), which clashes with 이제 unless you’re talking about a past moment in a story.

Both work, with a nuance difference:

• 이제 깨끗해요 = Now it’s clean. (focus on the present state)
• 이제 깨끗해졌어요 = It has become clean now. (focus on the change)

If you want to highlight the transformation (messy → clean), 깨끗해졌어요 is very common.

이제 means now (often implying a change from before).
In this sentence it naturally sits before the result: …이제 깨끗해요.
You can also say 이제 방을 청소해서 깨끗해요, but that tends to sound like now I’m cleaning it (these days / at this moment) depending on context, so the original placement is clearer.

All are used, with slightly different “feel”:

• 방을 청소하다 = straightforward clean the room
• 방 청소하다 = common spoken shortcut meaning do room-cleaning
• 방 청소를 하다 = very common, using the noun 청소
  • 하다

Your sentence uses a clean, standard pattern: N을 청소하다.

That’s about speech level:

• 깨끗해요 = polite, common everyday style
• 깨끗합니다 = more formal (presentations, announcements, writing)
• 깨끗해 = casual (to friends, family)

So 깨끗해요 is a safe default in most situations.

It’s ambiguous (and that’s normal in Korean). It can mean:

• I/we cleaned the room, so now it’s clean, or
• more generally The room got cleaned, so now it’s clean (if the doer isn’t important)

If you want to force I: 제가 방을 청소해서 이제 깨끗해요.
If you want to sound more passive: 방을 청소해 놓아서 이제 깨끗해요 (emphasizes the cleaned state being left as-is).

It’s pronounced smoothly as 청소해서 (roughly: cheong-so-hae-seo).
The 하 + 여서 contracts to 해서:

• underlying: 청소하 + 여서
• common form: 청소해서

This 해서 contraction is extremely common (e.g., 공부해서, 일해서, 준비해서).