Kannst du bitte den Satz kopieren und in das Dokument einfügen?

Because this is a yes/no question in German. In a yes/no question, the conjugated verb comes first.

• Kannst du ... ? = Can you ... ?

If it were a statement, the word order would change:

• Du kannst den Satz kopieren und in das Dokument einfügen.
  = You can copy the sentence and paste it into the document.

Literally, Kannst du means Can you. But in this sentence, it is being used as a request, not as a real question about ability.

So:

• Kannst du bitte ... ? often means Can you please ... ?

In English, we also do this: Can you pass the salt? is usually a request, not a test of ability.

A slightly more polite version in German would be:

• Könntest du bitte ... ? = Could you please ... ?

Du is the informal word for you when speaking to one person.

So this sentence is addressed to:

• a friend
• a family member
• a child
• a colleague in an informal setting

If you wanted the formal version, you would say:

• Können Sie bitte den Satz kopieren und in das Dokument einfügen?

Notice that Sie is capitalized when it means formal you.

Bitte means please here. It makes the request sound more polite.

• Kannst du den Satz kopieren ... ? = less polite / more direct
• Kannst du bitte den Satz kopieren ... ? = more polite

In German, bitte is quite flexible and can appear in different places, but in this sentence its position is very natural.

Because den Satz is in the accusative case. It is the direct object of kopieren.

The noun is:

• der Satz = nominative singular
• den Satz = accusative singular

Since Satz is masculine, the article changes:

• nominative: der
• accusative: den

So:

• der Satz = the sentence
• ich kopiere den Satz = I copy the sentence

Here, Satz means sentence.

So den Satz kopieren means to copy the sentence.

Depending on context, Satz can have other meanings in German, but for most learners the main meaning is sentence in language.

Because German uses a different word order from English when there is a modal verb like können.

In this sentence:

• kannst is the conjugated modal verb
• kopieren and einfügen stay in the infinitive
• the infinitives go to the end of the clause

So the structure is roughly:

• Kannst
  • subject + other elements + kopieren und einfügen

This is very normal German word order with modal verbs.

Yes, einfügen is a separable verb.

Its base form is:

• einfügen = to insert / to paste

When a separable verb is used with a modal verb, it usually stays unsplit in the infinitive:

• Kannst du ... einfügen?

But without a modal verb, it separates:

• Du fügst den Satz in das Dokument ein.

So:

• with modal: einfügen
• without modal: fügt ... ein

Because in can take either the accusative or the dative, depending on meaning.

Here it expresses direction/movement into something:

• in das Dokument einfügen = paste into the document

That requires the accusative:

• das Dokument stays das Dokument in accusative because it is neuter
• so: in das Dokument

But im Dokument means in the document in the sense of location, not movement:

• Der Satz steht im Dokument. = The sentence is in the document.

So:

• in das Dokument = into the document
• im Dokument = in the document

Yes. Ins is just the contraction of in das:

• in das Dokument
• ins Dokument

Both are correct. Ins Dokument is often more natural in everyday German.

So this sentence could also be:

• Kannst du bitte den Satz kopieren und ins Dokument einfügen?

Because all nouns are capitalized in German.

So in this sentence, these words are capitalized because they are nouns:

• Satz
• Dokument

This is one of the most noticeable spelling differences between German and English.

Not in normal standard German. In this kind of sentence, the infinitives usually come at the end, and the object comes before them.

So the natural structure is:

• Kannst du bitte den Satz kopieren und in das Dokument einfügen?

German generally prefers:

• verb in first position for the yes/no question
• subject next
• objects and other phrases in the middle
• infinitives at the end

So kopieren den Satz would sound wrong here.

Yes, in this context einfügen usually means paste.

So:

• kopieren = copy
• einfügen = paste / insert

In computer contexts, this pair is very common:

• Kopieren und einfügen = copy and paste

So even though einfügen literally has the sense of insert, in this sentence paste is the natural English meaning.