muni an yeollimyeon sonjabireul gyesok danggiji malgo jigwonege meonjeo mureobwayo.

Because the verb here is 열리다, not 열다.

• 문이 열리다 = the door opens / the door gets opened
• 문을 열다 = to open the door

With 열리다, the door is treated as the subject, so it takes -이/가.
That is why 문이 안 열리면 means if the door doesn’t open.

They are related, but they work differently:

• 열다 = to open (something)
  
  • 문을 열다 = open the door
• 열리다 = to open / to be opened
  
  • 문이 열리다 = the door opens / is opened

In this sentence, the focus is not on who opens the door. The focus is on the situation: the door won’t open. So 열리다 is the natural choice.

-면 means if or when, depending on context.

Here it introduces a condition:

• 안 열리면 = if it doesn’t open

In instructions like this, -면 often feels like if this happens, then do this.

Because 안 열면 would mean if someone doesn’t open it, while 안 열리면 means if it doesn’t open.

That is an important difference:

• 문이 안 열리면 = if the door doesn’t open
• 문을 안 열면 = if someone doesn’t open the door

The sentence is describing the door’s condition, not someone’s action, so 안 열리면 is correct.

Sometimes, yes, but the nuance changes a little.

• 안 열리면 = if it doesn’t open
• 못 열리면 = if it can’t open / if it cannot be opened

안 is a simple negation.
못 emphasizes inability.

For a stuck door, both can make sense in real life, but 안 열리면 is a very natural everyday way to say if the door won’t open.

Because 당기다 is a transitive verb, meaning it takes an object.

• 손잡이를 당기다 = pull the handle

The handle is the thing being pulled, so it gets the object marker -을/를.

계속 means continuously, repeatedly, or keep on.

So:

• 당기지 말고 = don’t pull it
• 계속 당기지 말고 = don’t keep pulling it

It adds the idea of repeated or ongoing action.

-지 말고 means don’t do X, and instead do Y.

So:

• 계속 당기지 말고 직원에게 먼저 물어봐요

means:

• Don’t keep pulling it; instead, ask a staff member first.

This pattern is very common when giving an alternative:

• 가지 말고 기다리세요 = Don’t go; wait instead.
• 혼자 하지 말고 물어보세요 = Don’t do it alone; ask instead.

-에게 marks the person an action is directed toward, similar to to in English.

So:

• 직원에게 물어봐요 = ask a staff member

With people, Korean often uses:

• 에게 = standard/written/polite neutral
• 한테 = more casual
• 께 = honorific

So you could also hear:

• 직원한테 물어봐요 = more casual
• 직원께 물어보세요 = more respectful

먼저 means first or before anything else.

It shows order:

• first ask the staff
• rather than continuing to pull the handle

So it makes the instruction sound like: Before doing anything else, ask an employee.

물어봐요 comes from 묻다 (to ask) + -아/어 보다.

The pattern -아/어 보다 often means try doing or check by doing.
So 물어보다 is like ask and see / check by asking.

In real Korean, 물어보다 is extremely common and often sounds very natural in situations like this. It can feel a bit softer and more practical than plain 묻다.

So:

• 물어요 = ask
• 물어봐요 = ask / try asking / check with

In this sentence, 물어봐요 fits the situation very well.

Because 묻다 is a ㄷ irregular verb.

When 묻다 is followed by a vowel, the ㄷ changes to ㄹ:

• 묻다 → 물어요
• 묻다 + 어 보다 → 물어보다
• 물어보다 → 물어봐요

So 물어봐요 is the correct conjugated form.

It is the polite informal style, often called the -아요/어요 style.

That means it is polite, but still natural and conversational. It is very common in spoken Korean and friendly written instructions.

You might compare:

• 물어봐요 = polite, conversational
• 물어보세요 = polite and more directly instructive
• 물어보십시오 = very formal

So this sentence sounds polite and natural, like a spoken instruction or a customer-facing notice.