piryo eobsneun sajineun sakjehaessjiman i munseoneun namgyeo dugo sipeo.

필요 없는 사진 literally means something like photos that are not needed.

It is built like this:

• 필요 = need, necessity
• 없다 = to not exist / to not have
• 없는 = the noun-modifying form of 없다
• 사진 = photo

So:

• 필요 없다 = to be unnecessary / to not be needed
• 필요 없는 사진 = unnecessary photos

A useful thing to notice is that Korean often uses this kind of noun-modifying clause before a noun, where English might use an adjective like unnecessary.

Because 없다 is being used to describe the noun 사진.

In Korean, when a descriptive word or clause directly modifies a noun, it usually changes form:

• 없다 → 없는

So:

• 필요 없다 = it is unnecessary
• 필요 없는 사진 = photos that are unnecessary

This is similar to how verbs and adjectives change before nouns in Korean.

Here 은/는 gives a topic/contrast feeling.

The sentence is contrasting two things:

• 필요 없는 사진은 삭제했지만 = As for the unnecessary photos, I deleted them, but...
• 이 문서는 남겨 두고 싶어 = this document, I want to keep

Using 은/는 here helps create the contrast:

• the photos → deleted
• this document → want to keep

If you used 을/를, the sentence would focus more simply on the direct object, but the contrast would be weaker.

삭제했지만 breaks down as:

• 삭제하다 = to delete
• 삭제했다 = deleted
• -지만 = but / although

So 삭제했지만 means deleted, but... or although I deleted...

In this sentence, -지만 connects two contrasting ideas:

• I deleted the unnecessary photos,
• but I want to keep this document.

It is a very common way to say but in Korean.

삭제하다 is a more formal or technical word meaning to delete.

• 삭제하다 often sounds appropriate for files, documents, photos, data, etc.
• 지우다 can also mean erase / delete / wipe off, and is more everyday and broad.

So in a sentence about photos and a document, 삭제하다 sounds natural, especially if the context is digital files.

남겨 두다 is a very common Korean construction.

It comes from:

• 남기다 = to leave, keep, set aside
• 두다 = to put, place, leave

When -아/어 두다 is attached to a verb, it often means:

• do something and leave it that way
• keep something in that state for later
• leave something as it is intentionally

So:

• 남기다 = to leave / keep
• 남겨 두다 = to leave something in place / keep it for later / leave it alone intentionally

In this sentence, 이 문서는 남겨 두고 싶어 means not just I want to leave this document, but more like I want to keep this document as it is or I want to leave this document undeleted.

Both are possible, but they feel a little different.

• 남기고 싶어 = I want to leave/keep it
• 남겨 두고 싶어 = I want to leave it there / keep it set aside / keep it as is

Adding 두다 gives a stronger nuance of:

• keeping something in a certain state
• leaving it untouched
• saving it for later

In this sentence, that nuance fits well because the speaker deleted some things but wants this document to remain.

-고 싶다 means to want to do.

So:

• 남겨 두고 싶어 = want to leave/keep it

Breakdown:

• 남겨 두다 = to keep / leave as is
• 남겨 두고 싶다 = to want to keep it
• 남겨 두고 싶어 = same meaning, but in informal speech style

This ending is used to express the speaker’s own desire.

Because this sentence is in a casual/informal style.

Compare:

• 싶어 = casual
• 싶어요 = polite
• 싶습니다 = formal

So the original sentence sounds like something you might say to a friend, family member, or someone you speak casually with.

A polite version would be:

• 필요 없는 사진은 삭제했지만 이 문서는 남겨 두고 싶어요.

Yes. Korean often leaves out the subject when it is understood from context.

The sentence naturally implies I:

• (나는) 필요 없는 사진은 삭제했지만 이 문서는 남겨 두고 싶어.

English usually needs the subject, but Korean often does not.

이 means this.

So:

• 문서 = document
• 이 문서 = this document
• 이 문서는 = as for this document

It points to a specific document, probably one visible in the situation or already known in the conversation.

Yes, that is a very natural translation.

A slightly more literal version would be:

• As for the unnecessary photos, I deleted them, but this document I want to leave/keep.

But in natural English, I deleted the unnecessary photos, but I want to keep this document is the best kind of translation.

The sentence can be divided into two parts:

1. 필요 없는 사진은 삭제했지만

   • As for the unnecessary photos, I deleted them, but...

2. 이 문서는 남겨 두고 싶어

   • as for this document, I want to keep it

So the full structure is basically:

• [first topic] + action + but + [second topic] + desired action

This is a very common Korean contrast pattern.