matigaeta bun ha sakuzyosuru mae ni, pasokon ni hozonsite oita hou ga ii.

In Japanese, a verb in plain form can directly modify a noun.

So 間違えた文 literally means the sentence that was gotten wrong or the sentence someone made a mistake on/in.

The past form 間違えた does not make the whole sentence past tense. It just describes the noun 文. This is the same kind of structure as:

• 昨日読んだ本 = the book I read yesterday
• 壊れたパソコン = the broken computer

So here, 間違えた文 is a noun phrase meaning something like a mistaken sentence or a sentence you got wrong.

Yes, there is a small nuance difference.

• 間違えた文 focuses on the act of someone making a mistake with that sentence.
• 間違った文 focuses more on the sentence being wrong/incorrect itself.

In many situations, they overlap, and both may be understandable. But in a learning context, 間違えた文 often sounds like the sentence you got wrong.

は marks 間違えた文 as the topic.

So the sentence is structured like:

As for mistaken sentences, before deleting them, it’s better to save them to your computer.

Using は gives a topic frame. It can also suggest mild contrast, like when it comes to wrong sentences... as opposed to other sentences.

With 前に, Japanese normally uses the dictionary form of a verb:

• 食べる前に = before eating
• 帰る前に = before going home
• 削除する前に = before deleting

That is because the action has not happened yet at that point.

By contrast:

• 削除した後に = after deleting

So 削除する前に is the normal and correct form for before deleting.

Here, に marks the destination or target location of the saved data.

So パソコンに保存する means to save it to/onto the computer.

Compare:

• パソコンに保存する = save it to the computer
• パソコンで保存する = save it using a computer

So に is used because the data ends up on/in the computer.

This comes from 保存しておく.

〜ておく often means:

• do something in advance
• do something and leave it that way for later use

So 保存しておく means save it in advance or save it and keep it saved.

In this sentence, that nuance is important: you should save it before deleting it, as a precaution.

Because the common advice pattern is:

• Vたほうがいい = had better / should
• Vないほうがいい = had better not / shouldn’t

So with 保存しておく, the past plain form is 保存しておいた, and that becomes:

保存しておいたほうがいい = it would be better to save it in advance

This does not mean the whole sentence is talking about the past. It is just the normal grammar pattern for giving advice.

The object is omitted because it is clear from context.

The thing being saved is 間違えた文 or possibly the file/document containing it.

Japanese often leaves out objects when they are obvious. In English, you would usually say save it, but in Japanese, leaving out それを is very natural here.

Japanese often omits the subject when it is understood from context.

Here, the implied subject is probably you, or possibly people in general.

So the sentence naturally feels like:

You should save mistaken sentences to your computer before deleting them.

It breaks down like this:

• 間違えた文は = as for the mistaken sentence(s)
• 削除する前に = before deleting
• パソコンに = to the computer
• 保存しておいたほうがいい = it would be better to save

So the logic is:

As for mistaken sentences, before deleting them, it’s better to save them to your computer.

Japanese often puts the topic first, then time-related phrases, and then the main statement at the end.