sseuregitong yeope meonjiga manhaseo meonjeo chiwoya hae.

옆에 marks a location: next to / beside.

So 쓰레기통 옆에 먼지가 많아서 means because there is a lot of dust next to the trash can.

If you used 옆에서, it would sound more like at the side of / beside it (as the place where an action happens). That particle is often used when something is being done at that location.

• 옆에 먼지가 많다 = There is a lot of dust next to it.
• 옆에서 청소하다 = Clean beside it / clean at that spot.

Here the sentence is describing where the dust is, so 옆에 is the natural choice.

Because 많다 works like an adjective meaning to be many / to be a lot and the thing that is abundant takes the subject marker 이/가.

So:

• 먼지가 많다 = There is a lot of dust / Dust is plentiful

Using 먼지를 would be wrong here because 많다 does not take its noun as a direct object.

Compare:

• 사람이 많다 = There are many people
• 문제가 많다 = There are many problems
• 먼지가 많다 = There is a lot of dust

Here -아서/어서 connects two clauses and means because, or sometimes just shows that one situation leads naturally to the next.

So:

• 먼지가 많아서 먼저 치워야 해
• Because there is a lot of dust, we have to clean up first

In everyday Korean, -아서/어서 is very common for giving a reason in a natural, conversational way.

A similar version would be:

• 먼지가 많으니까 먼저 치워야 해

That also means because there is a lot of dust, we have to clean up first, but -니까 can sound a bit more direct or explanatory.

치워야 해 means have to clean up / have to put away / have to clear away.

It comes from:

• 치우다 = to clean up, clear away, put away
• -어야 하다 = have to, must

So:

• 치우다 → 치워야 하다 → 치워야 해 in casual speech

This expression shows necessity or obligation.

Examples:

• 방을 치워야 해 = I have to clean up the room.
• 이거 치워야 해 = We have to put this away.

In your sentence, it means something like we need to clean that area up first.

This is a conjugation pattern.

The verb stem is 치우-. When adding -어야 하다, it becomes:

• 치우 + 어야 하다 → 치워야 하다

This happens because 우 + 어 often contracts to 워.

Similar examples:

• 세우다 → 세워요
• 채우다 → 채워요
• 치우다 → 치워요

So 치워야 해 is just the natural conjugated form of 치우다 plus have to.

The object is omitted, which is very common in Korean.

From context, it probably means one of these:

• clean up the dust
• clean up that area
• clear up the space next to the trash can

Korean often leaves out words that are obvious from the situation. So even though there is no explicit object like 먼지를 or 거기를, listeners can understand it from context.

If you wanted to say it more explicitly, you could say:

• 쓰레기통 옆에 먼지가 많아서 먼지를 먼저 치워야 해.
• Because there is a lot of dust next to the trash can, we have to clean the dust up first.

But the shorter original sentence sounds natural in conversation.

먼저 means first.

It tells you the order of actions: before doing something else, this cleaning needs to happen first.

So the sentence implies something like:

• There is a lot of dust next to the trash can, so we need to clean that up first.

It often appears before the verb it modifies:

• 먼저 먹어. = Eat first.
• 먼저 가세요. = Please go first.
• 먼저 치워야 해. = We have to clean up first.

Yes. 해야 해 is casual, informal speech.

A more polite version would be:

• 쓰레기통 옆에 먼지가 많아서 먼저 치워야 해요.

A more formal/written style could be:

• 쓰레기통 옆에 먼지가 많아서 먼저 치워야 합니다.

So the levels are roughly:

• 치워야 해 = casual
• 치워야 해요 = polite conversation
• 치워야 합니다 = formal

Yes. 쓰레기통 literally breaks down as:

• 쓰레기 = trash, garbage
• 통 = container, bin, container-like vessel

So 쓰레기통 means trash can, garbage can, or bin.

This is a very common Korean compound noun.

Literally, it means because there is a lot of dust. By itself, 많다 just states quantity.

But in this sentence, the full context makes it sound like a reason for action. So it naturally implies that the amount of dust is enough to require cleaning.

In other words:

• 먼지가 많다 = There is a lot of dust.
• 먼지가 많아서 먼저 치워야 해 = There is a lot of dust, so we need to clean up first.

So the sense of this is a problem comes from the whole sentence, not from 많다 alone.

Yes, but the nuance is a little different.

• 치우다 = clean up, clear away, put away, tidy up
• 청소하다 = clean

So:

• 먼지가 많아서 먼저 치워야 해 sounds like we need to clear/clean up that area first
• 먼지가 많아서 먼저 청소해야 해 sounds more directly like we need to clean first

Both can work, but 치우다 often feels a bit broader and more practical, especially in everyday speech.

Yes, the subject is omitted, which is normal in Korean.

치워야 해 does not explicitly say I, we, or you. Korean often leaves that out when the context makes it clear.

Depending on the situation, it could mean:

• I have to clean up first
• We have to clean up first
• You have to clean up first

In English, you usually need to choose a subject, but Korean often does not.

It is pronounced more like 마나서 in natural speech.

That is because the ㅎ in 많- is not strongly pronounced here, and the sound changes smoothly into the following vowel.

So although it is written 많아서, what you hear is close to:

• 마나서

This kind of sound change is very common in Korean, so learners often notice that the spoken form sounds simpler than the spelling.