saendeureun pyeonhajiman orae georeumyeon dariga jom apayo.

은 is the topic particle. In 샌들은, it marks sandals as the topic: as for sandals or sandals, ...

It also gives a slight contrastive feeling here, which fits the rest of the sentence well:

샌들은 편하지만 ...
As for sandals, they’re comfortable, but ...

That contrast matches the but idea in 편하지만.

Because 샌들 ends in a consonant sound (-l), you use 은, not 는.

편하지만 comes from:

• 편하다 = to be comfortable / convenient
• -지만 = but / although

So:

• 편하다
• 편하지
• 편하지만

This means is comfortable, but ...

In this sentence, 하지만 is attached directly to the adjective stem, so it works like comfortable, but ...

A very similar sentence could also be written with a pause:

샌들은 편해요. 하지만 오래 걸으면 ...

That is more like: Sandals are comfortable. But if you walk a long time...

The original sentence is smoother and more natural as one sentence.

오래 is a very common adverb meaning for a long time.

So:

• 오래 걷다 = to walk for a long time
• 오래 기다리다 = to wait a long time
• 오래 살다 = to live a long time

Although 길게 can mean longly / at length / in a long way, it is not the natural choice here. For duration of time, Korean usually uses 오래.

So 오래 걸으면 naturally means if/when you walk for a long time.

걸으면 comes from the verb 걷다 (to walk) plus the conditional ending -으면.

• 걷다 = to walk
• irregular change: 걷- → 걸-
• 걸으면 = if/when (someone) walks

This is because 걷다 is a ㄷ irregular verb. In many forms before a vowel, ㄷ changes to ㄹ:

• 걷다
• 걸어요
• 걸으면
• 걸어서

So 오래 걸으면 means if you walk for a long time or when you walk for a long time.

In Korean, body parts with adjectives like 아프다 are usually marked with the subject particle 이/가, not the object particle 을/를.

So Korean says:

• 다리가 아파요 = my leg/legs hurt
• 머리가 아파요 = my head hurts
• 배가 아파요 = my stomach hurts

This is different from English, where we often think of the body part as the object: My legs hurt. In Korean, the body part is treated more like the subject of the condition.

So 다리가 아파요 is the normal pattern.

Grammatically, 다리 is singular in form, but Korean often does not mark plural unless it is necessary.

So 다리가 아파요 can mean:

• my leg hurts
• my legs hurt

In this sentence, because it is about walking in sandals for a long time, English speakers might naturally translate it as my legs hurt or even my feet start to hurt, depending on context.

Korean often leaves that kind of number information unstated unless it matters.

좀 literally means a little or somewhat, but in everyday Korean it often softens the sentence.

So 다리가 좀 아파요 means:

• my legs hurt a little
• my legs are kind of sore
• my legs hurt a bit

It can make the statement sound less blunt or less dramatic.

Compare:

• 다리가 아파요 = my legs hurt
• 다리가 좀 아파요 = my legs hurt a bit / are a little sore

In conversation, 좀 is very common for making statements sound more natural and less harsh.

Korean often leaves subjects unstated when they are understood from context.

So 오래 걸으면 다리가 좀 아파요 could mean:

• if I walk for a long time, my legs hurt
• if you walk for a long time, your legs hurt
• if one walks for a long time, one’s legs hurt

In this sentence, the most natural interpretation is often I or people in general, depending on the situation.

That is very normal in Korean. You do not need to state 저는 unless there is a reason to emphasize it.

Because the sentence has two different clauses with different grammatical roles.

1. 샌들은 편하지만
   Here, 샌들은 is the topic: As for sandals, they are comfortable, but...

2. 오래 걸으면 다리가 좀 아파요
   Here, 다리가 is the subject of 아파요: the legs hurt a bit

So the sentence structure is roughly:

• As for sandals, they are comfortable,
• but if you walk a long time, your legs hurt a bit.

This is very common in Korean: one noun can be the topic of the whole sentence, while another noun is the subject inside a later clause.

They are similar, but not exactly the same.

• 편하지만 = comfortable, but ...
• 편한데 = it’s comfortable, but / and / by the way ...

In this sentence, 편하지만 gives a clear contrast:

샌들은 편하지만 오래 걸으면 다리가 좀 아파요.
Sandals are comfortable, but if you walk a long time, your legs hurt a bit.

If you said 편한데, it could sound a little softer or more conversational, and the contrast might feel slightly less direct. But both can work depending on tone.

Yes. The sentence ends in -아요, so it is in the standard polite style:

아파요

The casual version would be:

샌들은 편하지만 오래 걸으면 다리가 좀 아파.

You might also hear slightly different casual phrasing in speech, but 아파 is the basic casual ending here.

So:

• Polite: 아파요
• Casual: 아파

Yes, it is natural. It sounds like a normal comment about footwear.

A Korean speaker might also say similar variations such as:

• 샌들은 편하지만 오래 걸으면 발이 아파요.
  Sandals are comfortable, but if you walk a long time, your feet hurt.

• 샌들은 편하긴 한데 오래 걸으면 다리가 좀 아파요.
  This adds a slightly conversational nuance: Sandals are comfortable, but if I walk a long time, my legs hurt a bit.

Your original sentence is perfectly natural and useful for learners because it shows several common patterns clearly.