Лучше сохранить резервную копию и отправить старые файлы в архив, чем потом всё искать заново.

Лучше here means it is better to... or better... than.... It is the comparative form of хорошо / хороший, but in this kind of sentence it works like a predicative adverb, not like an adjective.

So:

• Лучше сохранить... = It’s better to save...
• Лучший would mean the best as an adjective, for example лучший файл = the best file
• Лучше всего means best of all / it is best to, which is possible in some contexts, but here plain лучше is the normal choice

This sentence has the pattern:

• Лучше + infinitive ..., чем + infinitive / clause

So the basic structure is: Better to do X than do Y later.

After лучше, Russian often uses the infinitive to express a general recommendation or preferable action.

So:

• Лучше сохранить... = It is better to save...
• Лучше отправить... = It is better to send...

This is very common in Russian:

• Лучше подождать. = It’s better to wait.
• Лучше не спорить. = It’s better not to argue.

In your sentence, both infinitives depend on лучше:

• Лучше сохранить резервную копию
• и отправить старые файлы в архив

Together they mean: It’s better to save a backup copy and send the old files to the archive...

They are perfective because the sentence is about completing specific actions, not about an ongoing process.

• сохранять = to be saving / to save repeatedly / in general

• сохранить = to save successfully, as a completed act

• отправлять = to be sending / send regularly
• отправить = to send, complete the sending

Here the speaker means:

• make one backup copy
• move/send the old files to the archive

So perfective is natural, because the idea is do these things once, completely, before a problem happens.

If you used imperfective here, it would sound more like a general process or habit, not the single completed precaution the sentence recommends.

Because копию is the direct object of сохранить, so it takes the accusative case.

The dictionary form is:

• резервная копия = backup copy

But after сохранить (to save), you need the accusative:

• сохранить что? → резервную копию

Singular feminine adjectives and nouns change like this:

• nominative: резервная копия
• accusative: резервную копию

So this is just normal case marking for a feminine direct object.

It is accusative plural, but for inanimate masculine plural nouns, the accusative looks the same as the nominative.

So:

• nominative: старые файлы
• accusative: старые файлы

Since файлы are inanimate, the form does not change in the plural.

The phrase is the object of отправить:

• отправить что? → старые файлы

So grammatically it is accusative, even though it looks identical to nominative.

Because в архив expresses movement into something, not location in something.

Compare:

• отправить в архив = send to the archive / move into the archive
• хранить в архиве = store in the archive

With в:

• в + accusative often shows direction or destination
• в + prepositional often shows location

Here, отправить involves motion toward a destination, so Russian uses:

• в архив (accusative)

This is the second half of the comparison after лучше.

Pattern:

• Лучше X, чем Y = Better X than Y

So here:

• Лучше сохранить... и отправить..., чем потом всё искать заново.

Literally:

• Better to save... and send..., than later search for everything again.

The word чем means than in comparisons.

The word потом means later / afterwards.

The infinitive искать is used because it continues the same general better to do X than do Y pattern.

So the whole comparison is:

• better to take preventive action now
• than have to search for everything again later

Всё means everything here.

So:

• потом всё искать заново = later search for everything again

It refers generally to all the files or all the things you would need to locate if you did not organize them now.

A useful distinction:

• всё = everything
• все = all / everyone

Examples:

• Я всё знаю. = I know everything.
• Все файлы на месте. = All the files are in place.

Here it is всё, because the meaning is everything, not all files as a noun phrase.

Both can often be translated as again, but they are not always identical.

• снова = again, one more time
• заново = anew, from the beginning, all over again

In this sentence, искать заново suggests having to search all over again / start the search from scratch. That fits the context very well: if you do not back things up and archive old files, you may later have to redo the whole search process.

Compare:

• Я снова позвоню. = I’ll call again.
• Нам пришлось всё делать заново. = We had to do everything over again from scratch.

So заново is stronger and more specific than just снова.

Потом usually comes before the part of the sentence it modifies, and here it sets the time frame for the whole action:

• чем потом всё искать заново = than later have to search for everything all over again

Russian word order is flexible, but this is a very natural placement. It emphasizes the contrast between:

• doing something now
• dealing with the consequences later

You could move words around in Russian more than in English, but this order is the most straightforward and idiomatic here.

Yes. Russian often leaves out the subject in general statements like this.

English often says:

• It is better to save a backup...

Russian does not need a dummy subject like it. So:

• Лучше сохранить... literally is just Better to save...

The sentence is impersonal and general. It means something like:

• It’s better
• One should better
• You’d better

depending on how you want to translate it into natural English.

Yes. И simply connects the two infinitives:

• сохранить резервную копию
• отправить старые файлы в архив

So the speaker recommends both actions together as part of one good strategy.

This structure is very common:

• Лучше сделать A и сделать B, чем потом...

It does not imply a strict sequence as strongly as English sometimes does. It just means both are advisable. In practice, the order here is logical: first save a backup, then archive old files.

Yes, but it would change the style a little.

For example:

• Лучше сохранить резервную копию и отправить старые файлы в архив, чем потом искать всё заново.

That is almost the same as the original; only the word order of всё changes.

You could also say something more personal:

• Тебе лучше сохранить резервную копию и отправить старые файлы в архив...
• Вам лучше сохранить резервную копию...

That means You’d better save a backup copy...

The original version is neutral and general, which is why the infinitive structure works so well.