Nach dem Download speichere ich alles in der Cloud und setze ein Lesezeichen für später.

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

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

So:

• nach dem Download = after the download

This is a very common pattern in German:

• nach dem Essen = after the meal
• nach der Arbeit = after work
• nach dem Film = after the movie

Because the sentence starts with the phrase Nach dem Download. In German main clauses, the finite verb must be in second position.

So the structure is:

• Nach dem Download = position 1
• speichere = position 2
• ich = then comes the subject

That is why you get:

• Nach dem Download speichere ich ...

If the sentence started with the subject, it would be:

• Ich speichere nach dem Download alles in der Cloud ...

Both are grammatically possible, but the original version puts more emphasis on when it happens.

Yes. Download is a very common loanword in German, especially in tech contexts.

It is usually treated as a masculine noun:

• der Download
• dem Download
• des Downloads

German uses many English tech words, but they are fitted into German grammar, so they still take articles and case endings.

Because in is a two-way preposition. It can take:

• dative for location
• accusative for direction/movement toward somewhere

Here, in der Cloud describes where the data ends up being stored, so it is treated as a location:

• in der Cloud = in the cloud

Compare:

• Ich speichere alles in der Cloud. = I store everything in the cloud.
• Ich lade alles in die Cloud hoch. = I upload everything into the cloud.

With hochladen, the movement idea is stronger, so in die Cloud is very natural. With speichern, German often uses in der Cloud.

Alles is the direct object of speichere:

• Ich speichere was? → alles

German word order is more flexible than English, but a very natural order here is:

• verb
• subject
• object
• adverbial phrase

So:

• speichere ich alles in der Cloud

You could sometimes move things around for emphasis, but the original order is very normal and natural.

It is in the accusative case, because it is the direct object of speichern.

• ich speichere alles = I save everything

With alles, the form does not change here, so you do not see a special ending. But grammatically, it is still accusative.

Yes, exactly. Ein Lesezeichen setzen is a normal German expression meaning to place/set a bookmark.

• das Lesezeichen = bookmark
• ein Lesezeichen setzen = to bookmark / to set a bookmark

This is similar to English tech language, where people also say set a bookmark less often, though bookmark is more common as a verb in everyday English.

In German, setzen is a very natural verb here.

In very informal digital contexts, some speakers do use English-based verbs, but ein Lesezeichen setzen is the standard and safest choice.

So for learners, the best expression is:

• ein Lesezeichen setzen

Another possible phrasing in some contexts is:

• etwas als Lesezeichen speichern

But the sentence you have is completely normal.

Für später means for later.

It tells you the purpose of the bookmark:

• I set a bookmark for later
• in other words, so I can return to it later

It is a very common phrase in German:

• Das hebe ich mir für später auf. = I’ll save that for later.
• Für später notieren? = Make a note of it for later?

In your sentence, it sounds natural and idiomatic.

Because the same subject applies to both verbs:

• speichere
• setze

So German can coordinate them with und without repeating the subject:

• ... speichere ich alles in der Cloud und setze ein Lesezeichen ...

This is just like English:

• I save everything in the cloud and set a bookmark ...

You could repeat ich, but it is not necessary:

• ..., und ich setze ein Lesezeichen ...

That version may sound slightly more separate or emphatic.

Because this is a normal coordination of two parts with und, and German usually does not put a comma before und in this kind of sentence.

So:

• ..., speichere ich alles in der Cloud und setze ein Lesezeichen ...

No comma is needed.

A comma might appear in more complex structures, but not in this straightforward one.

Because they are all nouns, and all nouns are capitalized in German.

So in this sentence:

• Download = noun
• Cloud = noun
• Lesezeichen = noun

This is one of the most noticeable features of written German.

Here, später works like an adverb and means later.

In für später, it is part of a fixed time expression:

• für später = for later

Compare:

• später = later
• ein später Termin = a late appointment

So it can behave differently depending on the sentence, but here it is not describing a noun directly.

They are in the present tense:

• ich speichere
• ich setze

German often uses the present tense for:

• habitual actions
• general statements
• step-by-step instructions
• near-future actions

So this sentence could mean:

• something the speaker usually does
• something the speaker is doing as part of a process
• something the speaker will do next

That is completely normal in German.

Yes. In natural usage, nach dem Download often means after the download is complete or once the download has happened.

German time expressions like this are often understood by context rather than with absolute precision.

So depending on context, it can sound like:

• after downloading
• after the download
• once the download is done

All of those are close in meaning.