Nach dem Download öffne ich die Datei und lese sie in Ruhe.

Because nach is a preposition that takes the dative case when it means after in a time expression.

• der Download = the download
• dative singular masculine = dem Download

So:

• nach dem Download = after the download

The article changes because of the case, not because the meaning changes.

Download is normally masculine in German: der Download.

That is why you get:

• nominative: der Download
• accusative: den Download
• dative: dem Download

In this sentence, it appears after nach, so it becomes dem Download.

Yes, both are possible, but the word order changes because German main clauses follow the verb-second rule.

In the sentence:

• Nach dem Download öffne ich die Datei ...

the first position is occupied by Nach dem Download, so the conjugated verb öffne must come next.

If you start with ich, then you would say:

• Ich öffne nach dem Download die Datei ...

Both are grammatical. Starting with Nach dem Download puts a little more focus on when the action happens.

This is because German main clauses usually place the finite verb in the second position.

Here, the first position is already taken by Nach dem Download, so the verb must come next:

• Nach dem Download → position 1
• öffne → position 2
• ich → after the verb

This is one of the most important word-order rules in German.

Datei is a feminine noun in German:

• die Datei = the file

In this sentence, die Datei is the direct object of öffne. Feminine nouns use die in both the nominative and accusative singular, so the form stays the same.

• nominative: die Datei
• accusative: die Datei

That is why you see die Datei here.

Because the subject is ich, and the verb must match the subject.

The verb is lesen = to read. Its present-tense forms include:

• ich lese
• du liest
• er/sie/es liest
• wir lesen
• ihr lest
• sie/Sie lesen

So with ich, the correct form is lese.

Yes, sie can mean several different things in German, which is why it can be confusing.

Here, sie is an accusative pronoun referring back to die Datei.

Since Datei is feminine singular:

• die Datei → sie

So:

• ich lese die Datei
• ich lese sie

In this sentence, sie means it, not she or they.

German pronouns reflect grammatical gender, not just natural gender.

Since Datei is feminine, German uses the feminine pronoun sie to refer back to it.

English says it for things, but German says:

• masculine noun → ihn / er
• feminine noun → sie
• neuter noun → es

So Datei is feminine, which is why the pronoun is sie.

In Ruhe is a very common expression meaning something like:

• calmly
• without rushing
• at leisure
• in peace
• without being disturbed

So lese sie in Ruhe means the speaker reads the file in a calm, unhurried way.

It is better learned as a fixed phrase than translated word-for-word.

Because in Ruhe is a fixed idiomatic expression.

German often uses certain noun phrases without an article in set expressions. Here, Ruhe does not mean a specific, countable the calm. Instead, it expresses a general state: calmness, peace, quiet.

So:

• etwas in Ruhe lesen
• etwas in Ruhe anschauen
• Lass mich in Ruhe

These are all common expressions.

Because two coordinated parts of a sentence joined by und usually do not need a comma.

Here the structure is:

• öffne ich die Datei
• und lese sie in Ruhe

The subject ich applies to both verbs, so this is a very normal coordination with und, and no comma is needed.

Because the same subject continues into the second verb phrase.

German often avoids repeating the subject when it is already clear:

• Nach dem Download öffne ich die Datei und lese sie in Ruhe.

You could technically repeat it in some contexts, but it would usually sound unnecessary here.

English works similarly:

• I open the file and read it not usually
• I open the file and I read it

No. Öffnen is a normal, non-separable verb.

That means it stays together:

• Ich öffne die Datei.
• Ich habe die Datei geöffnet.

Some learners wonder about this because many German verbs with prefixes are separable, but öffnen does not split.

Because German often uses the present tense for:

• habits
• instructions
• general sequences
• actions described in a neutral, everyday way

So Nach dem Download öffne ich die Datei und lese sie in Ruhe can mean something like:

• this is what I do after the download
• after the download, I open the file and read it

German does not need a special future form here.

Yes. German can express this idea in different ways, for example:

• Nach dem Download ...
• Nach dem Herunterladen ...

Both are possible. Download is a borrowed noun from English and is very common in everyday German, especially in technical contexts. Herunterladen is more purely German.

The sentence you were given sounds natural and modern.