jungyohan sajineun dareun poldeo-e baegeophago cheombupaireun dasi bonaesseo.

Here, 사진은 and 첨부파일은 both use the topic particle 은.

This does a couple of things:

• It marks each noun as something the speaker is talking about.
• It can create a slight contrast between the two items.

So the sentence feels like:

• As for the important photos, I backed them up to another folder,
• and as for the attached file, I sent it again.

Using 은 twice helps separate the sentence into two parallel parts.

Because those nouns are being presented as topics, not simply as direct objects.

Compare the difference:

• 중요한 사진은 다른 폴더에 백업하고...
  • As for the important photos...
• 중요한 사진을 다른 폴더에 백업하고...
  • more directly (I) backed up the important photos...

Korean often drops or changes particles depending on what the speaker wants to emphasize. Here, the sentence is structured around two topics, so 은 is natural.

중요한 is the noun-modifying form of 중요하다 (to be important).

When a descriptive verb/adjective modifies a noun in Korean, it changes form:

• 중요하다 → 중요한 사진
• literally: important photo(s)

So:

• 중요한 사진 = important photo / important photos

You cannot say 중요하다 사진 in normal Korean grammar.

Yes. 다른 comes from 다르다, which means to be different.

When used before a noun, it becomes 다른:

• 다른 폴더 = a different folder / another folder

So in this sentence:

• 다른 폴더에 = to another folder / in a different folder

In natural English, another folder is usually the best translation here.

에 marks a location or destination.

In this sentence:

• 다른 폴더에 백업하다 = to back up something to another folder

So 에 shows where the photos were backed up.

Depending on context, 에 can mean:

• to
• in
• at

Here, to another folder is the most natural interpretation.

-고 is a connector meaning and.

So:

• 백업하고 첨부파일은 다시 보냈어 = backed up ... and sent the attachment again

The first verb is put into the -고 form to connect it to the next action:

• 백업하다 → 백업하고

Only the final verb, 보냈어, carries the sentence-ending tense and speech level.

Yes, normally it does.

In Korean, when actions are connected with -고, the tense is often shown only on the final verb, and that tense usually applies to the whole sequence unless context suggests otherwise.

So:

• 백업하고 첨부파일은 다시 보냈어

is understood as:

• (I) backed up the photos and sent the attachment again.

Even though 백업하고 does not visibly show past tense, the full sentence is interpreted as past because of 보냈어.

다시 means again.

So:

• 다시 보냈어 = sent again / resent

It shows that the file had already been sent before, and the speaker sent it one more time.

보냈어 is the informal polite-neutral / casual ending style, often called 해체.

It comes from:

• 보내다 = to send
• past tense: 보냈어 = sent

This style is commonly used:

• with friends
• with younger people
• in diaries
• in casual messages

If you wanted a more polite version, you could say:

• 보냈어요

So the sentence in a more polite style would be:

• 중요한 사진은 다른 폴더에 백업하고 첨부파일은 다시 보냈어요.

Yes, the subject is omitted.

Korean often leaves out the subject when it is clear from context. In this sentence, the understood subject is usually:

• I
• or sometimes we, depending on context

So the full meaning is something like:

• I backed up the important photos to another folder and sent the attached file again.

You do not need to explicitly say 내가 unless you want to emphasize who did it.

It can mean either photo or photos.

Korean nouns usually do not have to mark singular vs. plural unless it is important. So:

• 중요한 사진은 could mean the important photo or the important photos

The same is true for 첨부파일은:

• it could mean the attached file or the attached files

You figure it out from context or translation.

Yes. It is a very common Korean verb built from the English loanword 백업 (backup) plus 하다.

So:

• 백업하다 = to back up

This is very common in modern Korean, especially for tech-related actions.

Similarly, 첨부파일 is also a common tech word:

• 첨부 = attachment
• 파일 = file
• 첨부파일 = attached file / attachment

So the sentence sounds very natural in everyday digital or office context.

Yes. A more literal breakdown is:

• 중요한 사진은 = as for the important photo(s)
• 다른 폴더에 = to another folder
• 백업하고 = backing up / and backed up
• 첨부파일은 = as for the attached file(s)
• 다시 = again
• 보냈어 = sent

So a close literal rendering would be:

• As for the important photos, I backed them up to another folder, and as for the attached file, I sent it again.

Natural English usually smooths this out a bit, but understanding the clause-by-clause structure is very helpful for Korean grammar.