waipaiga an doenikka deiteoreul sseoyo.

Here, 와이파이 is the thing that is or is not functioning, so it takes the subject marker 가.

• 와이파이가 안 돼요 = The Wi‑Fi doesn’t work
• It is not the object of an action, so 를 would not fit here.
• 은/는 could be used in some contexts for contrast, as in 와이파이는 안 되니까... if you want to emphasize as for the Wi‑Fi, it’s not working...

So 가 is the most neutral choice for stating that the Wi‑Fi is the thing in that condition.

In this sentence, 안 되다 means to not work, to not function, or to be unavailable.

So:

• 와이파이가 안 돼요 = The Wi‑Fi isn’t working
• It does not mean to not become here, even though 되다 often means to become

Korean uses 되다 in many expressions, and one very common one is:

• 안 돼요 = It doesn’t work / It’s not allowed / It won’t do

The exact meaning depends on context. With 와이파이, it clearly means isn’t working.

-니까 means because or since, and it often gives a reason for the speaker’s decision, judgment, or following action.

So:

• 와이파이가 안 되니까 데이터를 써요 = Because the Wi‑Fi isn’t working, I use mobile data

Why -니까 works well here:

• It connects a reason to the speaker’s response.
• It sounds natural when explaining why someone is doing something.

Comparison:

• -아서/어서 can also mean because, but -니까 often sounds a little more direct or explanatory in cases like this.
• 그래서 is a separate word meaning so, and it connects two full clauses more loosely:
  • 와이파이가 안 돼요. 그래서 데이터를 써요.
  • The Wi‑Fi isn’t working. So I use data.

All are possible, but -니까 is very natural here.

Yes. 쓰다 has several meanings, and context tells you which one is meant.

Common meanings of 쓰다:

• to write
• to use
• to wear (for some items, like glasses or a hat)

In this sentence:

• 데이터를 써요 = I use data / I’m using data

Because the object is 데이터, the meaning is clearly use, not write.

를 marks the direct object of the verb.

Here, the verb is 쓰다 = to use, and the thing being used is 데이터.

So:

• 데이터를 써요 = use data

This is a straightforward object-marker pattern:

• 물을 마셔요 = drink water
• 휴대폰을 써요 = use a phone
• 데이터를 써요 = use data

In everyday Korean, 데이터 often means mobile data when talking about phones, Wi‑Fi, and internet usage.

So in this sentence, learners should understand it as:

• mobile data
• cellular data

Even though the word literally comes from English data, the real-life meaning here is specifically phone data usage.

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

So 데이터를 써요 can mean:

• I use data
• We use data
• People use data

In most everyday situations, it is understood from context that the speaker means I.

This is very normal in Korean. Pronouns like 저, 나, 우리 are often omitted unless needed for emphasis or clarity.

It can mean either, depending on context, but most naturally it suggests a current or practical response:

• Since the Wi‑Fi isn’t working, I’m using data

However, Korean present tense -아요/어요 is broad. It can also express:

• a general habit
• a current action
• a usual reaction

So this sentence could also mean:

• When the Wi‑Fi doesn’t work, I use data

If you want to make the right now meaning extra clear, Korean often relies on context rather than changing the verb form.

Korean very often puts the reason first and the result/action second, especially with endings like -니까.

So the natural structure is:

• 와이파이가 안 되니까 = because the Wi‑Fi doesn’t work
• 데이터를 써요 = I use data

This order is standard because -니까 attaches to the reason clause and prepares the listener for what comes next.

You generally would not keep exactly the same grammar and reverse it naturally in one sentence. Instead, if you want a different structure, you might rephrase:

• 데이터를 써요. 와이파이가 안 되니까요.
• I use data, because the Wi‑Fi isn’t working.

But the original order is the most typical.

The sentence is in informal polite style, also called the -요 style.

• 써요 is the polite present form of 쓰다
• 안 되니까 contains 되다 plus -니까, and the final politeness of the whole sentence is mainly shown by the last verb 써요

So this sentence is appropriate for everyday polite conversation.

Compare:

• 와이파이가 안 되니까 데이터를 써요 = polite
• 와이파이가 안 되니까 데이터 써 = casual/plain conversation with someone close
• 와이파이가 안 되니까 데이터를 씁니다 = formal

Yes, 안 되다 can mean to be not allowed in other contexts. For example:

• 여기서 사진 찍으면 안 돼요 = You must not take pictures here

But with 와이파이, that meaning does not fit naturally. Wi‑Fi is not something that is usually forbidden in this structure; it is something that works or doesn’t work.

So in this sentence, the meaning is definitely:

• the Wi‑Fi isn’t working

A few natural translations would be:

• The Wi‑Fi isn’t working, so I’m using data.
• Since the Wi‑Fi isn’t working, I’m using mobile data.
• Wi‑Fi’s down, so I’m using my data.

Even though the Korean uses -니까, in natural English people often translate it as so rather than a stiff because.