jeoneun toegeungire pyeonuijeome deulleoseo mureul sagon haeyo.

저는 uses the topic particle 는, which presents I as the topic of the sentence: As for me, ...

In this sentence, the speaker is talking about a personal habit, so 는 feels natural. It gives a general, background statement about what the speaker usually does.

If you used 제가, it would sound more like the subject is being specifically identified or contrasted, such as answering Who does that? In this sentence, that is usually not the main point.

퇴근길 is a compound noun:

• 퇴근 = getting off work, leaving work
• 길 = road, way, route

So 퇴근길 literally means the way home from work or the trip home after work.

The particle 에 marks the time or occasion here, so 퇴근길에 means on the way home from work.

They are doing two different jobs:

• 퇴근길에: 에 marks the time/occasion or contextual setting, roughly on the way home from work
• 편의점에: 에 marks the destination/location involved with 들르다, because 들르다 means to stop by somewhere

So the sentence structure is basically:

• on the way home from work
• to a convenience store
• stopping by
• I tend to buy water

Using 에 twice is completely normal because each one belongs to a different phrase.

들러서 comes from the verb 들르다, which means to stop by or to drop in.

Its form changes like this:

• dictionary form: 들르다
• connective form: 들러서

This is not from 들다. It is specifically from 들르다.

In this sentence, 들러서 connects two actions:

1. stopping by the convenience store
2. buying water

So it means something like stop by a convenience store and buy water.

This is just how 들르다 conjugates in natural Korean.

Although learners may expect something like 들르어서, Korean usually contracts it to 들러서. This contracted form is the normal one used in everyday speech and writing.

So:

• 들르다 → 들러요
• 들르다 → 들러서

This is a common kind of vowel contraction in Korean conjugation.

Here, -서 links the first action to the second action. It often means and then, so, or after doing depending on context.

In this sentence, it connects:

• 편의점에 들러서
• 물을 사곤 해요

The idea is: I stop by the convenience store and buy water.

It does not necessarily strongly emphasize cause here. It mainly connects the actions in sequence.

-곤 해요 expresses a repeated or habitual action. It often has the nuance of tend to, often, or used to regularly.

So:

• 물을 사요 = I buy water
• 물을 사곤 해요 = I tend to buy water / I often buy water

This makes the sentence sound less like a single event and more like a recurring habit. It is a very natural way to talk about something you do from time to time or regularly in a certain situation.

No. They are different.

• -고 해요 usually means someone says that... when attached after a quoted clause, or it can appear in other unrelated structures
• -곤 해요 is a grammar pattern showing habitual or repeated behavior

So in this sentence, 사곤 해요 is one fixed pattern:

• verb stem + 곤 하다

It means to do something habitually / from time to time.

You should treat -곤 하다 as its own expression rather than thinking of it as just -고 하다.

물 is the direct object of 사다 because it is the thing being bought.

• 물 = water
• 물을 = water + object particle

So 물을 사다 means to buy water.

The particle 을/를 marks what receives the action of the verb.

Yes. It ends with 해요, which is the standard polite style often called the -요 form.

That makes the whole sentence polite but still natural and conversational. It is appropriate in many everyday situations.

If you made it plain style, it could become:

• 저는 퇴근길에 편의점에 들러서 물을 사곤 해.

If you made it more formal, it could become:

• 저는 퇴근길에 편의점에 들러서 물을 사곤 합니다.

Yes, 저는 could be omitted if the subject is already clear from context.

Korean often leaves out subjects when they are understood. So in conversation, someone might simply say:

• 퇴근길에 편의점에 들러서 물을 사곤 해요.

That still sounds natural if it is obvious the speaker is talking about themselves.

However, keeping 저는 can be useful when:

• introducing your own habit
• contrasting yourself with someone else
• making the sentence clearer for emphasis

A helpful breakdown is:

• 저는 = as for me
• 퇴근길에 = on the way home from work
• 편의점에 = to a convenience store
• 들러서 = stopping by / and then stopping by
• 물을 = water
• 사곤 해요 = tend to buy

So the flow is:

As for me, on my way home from work, I tend to stop by a convenience store and buy water.

This is a very typical Korean structure: topic + time/context + place + action link + object + main verb.