jigeum eunhaeng aebe jeopsokhaeseo gyejwa janaegeul hwaginhaneun jungiya.

Because 접속하다 usually takes 에 to mark the place, service, or system you connect to.

• 은행 앱에 접속하다 = to access/connect to the banking app
• 웹사이트에 접속하다 = to access a website
• 인터넷에 접속하다 = to connect to the internet

So here, 은행 앱에 means to the banking app or more naturally in English, the banking app as the thing being accessed.

접속해서 comes from 접속하다 = to connect/access/log in, plus -아서/어서, which links actions.

So:

• 접속해서 = connect/access/log in and then...

In this sentence, it connects two actions:

1. access the banking app
2. check the account balance

It can sound like simple sequence, but in real usage it often just links closely related actions smoothly, like by accessing the app or after logging in.

Both can mean I’m checking or I’m in the middle of checking, but there is a nuance.

• 확인하고 있어 = I am checking
• 확인하는 중이야 = I am in the middle of checking / I’m currently engaged in checking

-는 중이다 emphasizes that the action is ongoing right now, often a bit more explicitly than -고 있다.

So:

• 지금 계좌 잔액을 확인하고 있어 = I’m checking my account balance now.
• 지금 계좌 잔액을 확인하는 중이야 = I’m in the middle of checking my account balance right now.

The sentence you gave sounds slightly more deliberate about the ongoing process.

It breaks down like this:

• 확인하다 = to check/confirm
• 확인하는 = checking / that is checking
  
  • this is the verb stem used before a noun-like expression
• 중 = middle, midst
• 이다 = to be
• 중이야 = casual spoken form of 중이다

So literally, 확인하는 중이야 means something like:

• I’m in the middle of checking

This pattern is very common:

• 먹는 중이야 = I’m eating / I’m in the middle of eating
• 공부하는 중이야 = I’m studying
• 전화하는 중이야 = I’m on the phone / I’m making a call

계좌 잔액 is a noun compound.

• 계좌 = account
• 잔액 = remaining amount, balance

Together:

• 계좌 잔액 = account balance

Korean often combines nouns like this very naturally, without needing extra words like of.

Other similar examples:

• 은행 계좌 = bank account
• 신용카드 결제 = credit card payment
• 휴대폰 번호 = phone number

So 계좌 잔액을 확인하다 means to check the account balance.

을/를 marks the direct object of the verb.

Here:

• 계좌 잔액을 = the account balance
• 확인하다 = to check

So 계좌 잔액을 확인하다 means to check the account balance.

The object marker is used because 확인하다 directly acts on 계좌 잔액.

중이야 is casual, informal speech.

It would usually be used with:

• friends
• close family
• someone younger
• casual texting

More polite versions would be:

• 지금 은행 앱에 접속해서 계좌 잔액을 확인하는 중이에요.
• 지금 은행 앱에 접속해서 계좌 잔액을 확인 중입니다.

Roughly:

• 중이야 = casual
• 중이에요 = polite everyday
• 중입니다 = formal

Yes, -는 중이야 already strongly suggests an ongoing action, so 지금 is not strictly necessary.

But 지금 adds emphasis and makes the timing extra clear:

• 지금 = now, right now

Compare:

• 은행 앱에 접속해서 계좌 잔액을 확인하는 중이야.
  = I’m checking the account balance through the banking app.
• 지금 은행 앱에 접속해서 계좌 잔액을 확인하는 중이야.
  = I’m checking the account balance right now.

Adding 지금 is very natural in speech.

Yes, the subject is omitted, which is very common in Korean.

From context, the sentence usually means:

• I’m currently accessing the banking app and checking my account balance.

Korean often leaves out subjects like I, you, or he/she when they are obvious from context.

If you wanted to include it, you could say:

• 나는 지금 은행 앱에 접속해서 계좌 잔액을 확인하는 중이야.

But in everyday conversation, leaving out 나는 is more natural unless you need emphasis.

It usually presents 접속하다 as the earlier or accompanying action that leads into the main action, 확인하는 중이야.

In normal interpretation:

• the person has accessed or logged into the app
• and is now in the process of checking the balance

So the ongoing focus is on 확인하는 중이야, not on 접속해서.

That said, in real life the two actions are closely connected, so the sentence can feel like:

• I’m on the banking app checking my account balance right now

rather than a sharply separated first I logged in, then I checked.

Yes, depending on what you want to emphasize.

• 접속하다 = to access/connect to a service, app, website, network
• 로그인하다 = to log in specifically

So:

• 은행 앱에 접속해서 = by accessing/opening the banking app
• 은행 앱에 로그인해서 = by logging into the banking app

If the important idea is just entering the app environment, 접속해서 is fine.
If you specifically want to say after logging in, then 로그인해서 may be more precise.

Yes. 앱 is a very common loanword in Korean for app.

• 은행 앱 = banking app / bank app

This kind of noun combination is very natural. You may also hear:

• 뱅킹 앱 = banking app
• 은행 어플 = bank app
  
  • 어플 comes from application, though 앱 is very common and modern

So 은행 앱에 접속하다 sounds natural.

Yes. 확인하다 is a very common verb with a range like:

• to check
• to verify
• to confirm

The exact English translation depends on context.

In this sentence:

• 계좌 잔액을 확인하다 = to check the account balance

But in other contexts:

• 예약을 확인하다 = to confirm a reservation / check a reservation
• 사실을 확인하다 = to verify the facts

So 확인하다 is broader than just one English word.