Když najdu správný soubor, hned ti ho pošlu.

Here když means when: When I find the right file, I’ll send it to you immediately.

In Czech, když can also mean if or whenever in other contexts, but in this sentence the natural meaning is a future when/once.

Najdu is from the perfective verb najít = to find.

In Czech, perfective verbs do not normally form the future with budu. Their present-looking forms are used with future meaning:

• najdu = I will find / I find
• pošlu = I will send / I send

So Když najdu... literally looks like When I find..., but it refers to the future: When I find...

By contrast, budu hledat means I will be looking / searching, which focuses on the process, not the completed result.

They are not the same:

• hledat = to look for, to search for
• najít = to find

So:

• Když budu hledat správný soubor... = When I’m looking for the right file...
• Když najdu správný soubor... = When I find the right file...

Your sentence uses najdu because the speaker means the moment the file is successfully found.

Najdu is the 1st person singular form of najít.

So it means I find / I will find.

A few forms of najít are:

• najdu = I will find
• najdeš = you will find
• najde = he/she/it will find
• najdeme = we will find

It is a common verb with a stem change, so it is worth memorizing as a whole verb.

Správný soubor is in the accusative singular, because it is the direct object of najdu.

• soubor = file
• správný = correct, right

Since soubor is a masculine inanimate noun, the accusative singular looks the same as the nominative singular:

• nominative: správný soubor
• accusative: správný soubor

So even though the case is accusative, the form does not change here.

It can mean both, depending on context, but very often in modern Czech it means a computer file.

So in this sentence, most learners would naturally understand správný soubor as the correct file on a computer, unless context suggests a paper file or dossier.

Because adjectives must agree with the noun they describe.

Soubor is:

• masculine
• singular
• inanimate

So the adjective takes the matching masculine singular form:

• správný soubor

And because masculine inanimate accusative singular is the same as nominative singular, the adjective still stays správný here.

Hned means immediately, right away, or at once.

So:

• hned ti ho pošlu = I’ll send it to you right away

It adds the idea that the speaker will not delay.

Because Czech expresses both to you and it with short pronoun forms here:

• ti = to you (dative)
• ho = it / him (accusative)

So:

• pošlu ti ho = I’ll send it to you

English uses word order and separate words. Czech often uses short unstressed pronouns like this.

Ti is the short, unstressed form of to you.
Tobě is the full, stressed form.

In a neutral sentence, Czech usually prefers the short form:

• Pošlu ti ho. = neutral, natural
• Pošlu tobě ho. = not natural
• Pošlu ho tobě. = possible only with strong emphasis, like I’ll send it to YOU

So ti is the normal choice here.

Ho can mean him, but it can also mean it when it refers to a masculine noun.

Since soubor is masculine, Czech can refer back to it with ho:

• soubor → ho

So in this sentence, ho means it, not him.

A fuller, more formal variant is jej, but ho is very common in everyday Czech.

Because short unstressed pronouns like ti and ho usually go in the second position in the clause.

In hned ti ho pošlu:

• hned is the first element
• ti ho come right after it
• pošlu comes later

This is a very typical Czech pattern. These short words are often called clitics, and their position is more fixed than English learners expect.

So hned ti ho pošlu sounds natural, while hned pošlu ti ho sounds much less natural.

Pošlu is the 1st person singular of the perfective verb poslat = to send.

So it means I will send.

Like najdu, it has a present-looking form with future meaning because it is perfective.

Compare:

• pošlu = I’ll send (one completed sending)
• budu posílat = I’ll be sending / I’ll send repeatedly

Here the speaker means one completed action, so pošlu is the right choice.

Because Když najdu správný soubor is a subordinate clause, and in Czech subordinate clauses are separated by commas.

So:

• Když najdu správný soubor, hned ti ho pošlu.

This comma is required in standard Czech spelling.

Yes, you often can:

• Až najdu správný soubor, hned ti ho pošlu.

This also means When/Once I find the right file, I’ll send it to you immediately.

A rough difference is:

• když = when / whenever / if, broader and very common
• až = when / once, often clearly future-oriented

In this sentence, až is also very natural. Když is not wrong at all; it just has a slightly broader feel.

Yes, it is completely natural.

A very idiomatic English translation would be:

• When I find the right file, I’ll send it to you right away.

Or:

• As soon as I find the right file, I’ll send it to you.

The Czech sentence is short, normal, and something a native speaker could easily say in everyday conversation.