Kiedy się zaloguję, od razu pobiorę ten plik.

They are future in meaning, even though their forms look like present-tense endings.

That is because both verbs are perfective:

• zalogować się = to log in / to log on (perfective: one completed action)
• pobrać = to download (perfective: one completed action)

In Polish, perfective verbs do not normally have a present tense with present meaning. Their so-called present forms are used to talk about the future:

• zaloguję się = I will log in
• pobiorę = I will download

So in this sentence:

• Kiedy się zaloguję = when I log in / when I have logged in
• od razu pobiorę ten plik = I will immediately download this file

Because the full verb is zalogować się, not just zalogować.

Many Polish verbs are used with się, and learners often need to memorize the whole expression as one unit. Here:

• logować się / zalogować się = to log in
• without się, the meaning changes or becomes unnatural in this context

So you should learn it as:

• zalogować się do systemu = to log into the system
• zaloguję się = I will log in

The się here does not mean myself in the English sense. It is just part of the verb.

Yes, się can often appear in different positions, but some placements sound more natural than others.

In your sentence:

• Kiedy się zaloguję, od razu pobiorę ten plik.

this is very natural.

You could also hear:

• Kiedy zaloguję się, od razu pobiorę ten plik.

That is also grammatical, but Kiedy się zaloguję... often sounds a bit smoother and more standard in neutral speech.

In general, się is a clitic-like word, so it often prefers an early position in the clause rather than being heavily stressed.

Because Polish uses the perfective verb form to express a completed future action.

English learners often expect something like I will be logged in or I will log in, but in Polish:

• zaloguję się already means I will log in
• pobiorę already means I will download

You use będę + infinitive/past-like form mainly with imperfective future forms, for example:

• będę pobierać plik = I will be downloading a file / I will download files (imperfective, ongoing or repeated)

But here the meaning is one completed login and one completed download, so perfective verbs are the natural choice.

Yes, this is completely normal.

In Polish, after kiedy when referring to the future, you often use a perfective verb form that has future meaning:

• Kiedy wrócę, zadzwonię. = When I come back, I’ll call.
• Kiedy skończę, odpocznę. = When I finish, I’ll rest.
• Kiedy się zaloguję, od razu pobiorę ten plik.

So even though the verb form looks present, it is understood as future because the verb is perfective.

This is actually not so different from English in subordinate time clauses, where English also often avoids will:

• When I log in, I’ll download the file.

Od razu means:

• immediately
• right away
• straight away

So:

• od razu pobiorę ten plik = I’ll download this file immediately / right away

It suggests there will be no delay between logging in and downloading the file.

A few examples:

• Napiszę od razu. = I’ll write back immediately.
• Powiedz mi od razu. = Tell me right away.

Because pobrać takes a direct object, and the direct object here is in the accusative case.

For a masculine inanimate singular noun like plik, the accusative form is the same as the nominative:

• nominative: ten plik
• accusative: ten plik

So:

• pobiorę ten plik = I will download this file

By contrast, tego pliku would usually be genitive, not the normal direct-object form here.

This is one of those places where Polish case is present, but the form happens to look unchanged.

Both are first person singular:

• zaloguję = I will log in
• pobiorę = I will download

The endings help show the subject, so Polish often drops the pronoun ja:

• (Ja) się zaloguję
• (Ja) pobiorę ten plik

Using ja is possible, but not necessary unless you want emphasis:

• Ja pobiorę ten plik, nie ty. = I’ll download the file, not you.

This is mainly a question of aspect.

• zaloguję się = perfective, one completed action
  I will log in
• będę się logować = imperfective future, process/repeated/habitual meaning
  I will be logging in / I will log in repeatedly

In your sentence, the point is that first the login will be completed, then the file will be downloaded. That is why zaloguję się fits better.

Similarly:

• pobiorę plik = I will download the file (one completed download)
• będę pobierać plik = I will be downloading the file (process, not necessarily completed)

Yes. In standard Polish spelling, a subordinate clause introduced by kiedy is separated by a comma.

So:

• Kiedy się zaloguję, od razu pobiorę ten plik.

This is the normal and correct punctuation.

The first part is the time clause:

• Kiedy się zaloguję

The second part is the main clause:

• od razu pobiorę ten plik

Yes. Polish word order is relatively flexible, though different orders can change emphasis.

Your sentence is very natural:

• Kiedy się zaloguję, od razu pobiorę ten plik.

Other possible versions include:

• Kiedy się zaloguję, pobiorę od razu ten plik.
• Od razu pobiorę ten plik, kiedy się zaloguję.
• Ten plik pobiorę od razu, kiedy się zaloguję.

But these may sound slightly different in focus. The original version is a good neutral choice:

1. first mention the condition/time point,
2. then say what will happen immediately after.

Because the sentence describes two single completed actions in sequence:

1. I log in
2. I download the file

Perfective aspect is ideal when you want to show that an action will happen once and will be completed.

Here are the aspect pairs involved:

• logować się / zalogować się
• pobierać / pobrać

The perfective forms are used because the speaker is not describing an ongoing process, but a clear result:

• once I have logged in,
• I will immediately download the file.

Yes, in many contexts you can.

Both kiedy and jak can mean when in everyday Polish. So:

• Kiedy się zaloguję, od razu pobiorę ten plik.
• Jak się zaloguję, od razu pobiorę ten plik.

Both are natural.

Very roughly:

• kiedy can sound a bit more neutral or standard
• jak is very common in speech

But in this sentence, both work well.

Not always. Its basic meaning is something like take / collect / obtain, depending on context.

In computer/tech contexts:

• pobrać plik = download a file
• pobrać aplikację = download an app

Outside technology, it can have other meanings, though in modern everyday Polish many learners first meet it in the sense of download.

So in your sentence, because of ten plik, the meaning download is completely clear.