Op kantoor gebruik ik een scanner om het contract op te sturen.

Dutch often puts a time/place expression at the beginning of the sentence when it sets the scene.

So:

• Op kantoor = At the office / In the office
• then the verb must come next: gebruik
• then the subject: ik

This is a very common Dutch pattern:

• Op kantoor gebruik ik ...
• Morgen ga ik ...
• In de trein lees ik ...

It gives a little extra emphasis to the location.

Because Dutch is a verb-second (V2) language in main clauses.

That means the finite verb must be in the second position. If something other than the subject comes first, the subject moves after the verb.

So:

• normal order: Ik gebruik een scanner.
• with a place expression first: Op kantoor gebruik ik een scanner.

The first whole chunk is Op kantoor, and the verb gebruik must come right after it.

Op kantoor is the normal idiomatic Dutch expression for at the office / at work.

Dutch uses certain prepositions in fixed expressions that do not always match English literally. A few common ones are:

• op school = at school
• op kantoor = at the office
• op straat = in the street / on the street

So this is something you largely learn as a set phrase.

In this phrase, op kantoor is an idiomatic expression meaning at the office / at work in a general sense.

Compare:

• Ik ben op kantoor. = I am at the office / at work.
• Ik ben op het kantoor van de directeur. = I am at the director’s office.

So:

• op kantoor = general, idiomatic
• op het kantoor = a specific office, more literal

Een means a/an, while de or het means the.

So:

• een scanner = a scanner, not a specific one
• de scanner = the scanner, a specific one already known in context

In this sentence, the speaker is talking about using a scanner as a tool, not identifying one particular scanner.

In Dutch, nouns take either de or het as their definite article.

Contract is a het-word, so:

• het contract
• een contract

Unfortunately, there is not always an obvious rule you can rely on, so many nouns simply have to be learned with their article.

A useful habit is to memorize nouns as a unit:

• het contract
• de scanner
• het kantoor

Om ... te is used to express purpose, often like in order to in English.

So:

• Ik gebruik een scanner om het contract op te sturen.
• literally: I use a scanner in order to send the contract off

In natural English, you often just translate it as to:

• I use a scanner to send the contract.

This structure is very common in Dutch when one action is done for the purpose of another.

Because opsturen is a separable verb.

The full verb is:

• opsturen = to send off / send in / mail

It consists of:

• op = prefix
• sturen = verb stem

When te is used with a separable verb, te goes between the prefix and the verb:

• opsturen
• op te sturen

More examples:

• aankomen → aan te komen
• meebrengen → mee te brengen
• uitzoeken → uit te zoeken

A separable verb is a verb made of a main verb plus a prefix that can split off in certain sentence patterns.

For example:

• infinitive: opsturen
• main clause: Ik stuur het contract op.
• with te: om het contract op te sturen
• past participle: Ik heb het contract opgestuurd.

This is a very important Dutch pattern, and it often causes confusion for English speakers because the pieces of the verb do not always stay together.

Because in the om ... te clause, op te sturen is the infinitive verb phrase, and objects usually come before that final verb group.

So Dutch structure is:

• om
  • other elements + infinitive at the end

Here:

• om het contract op te sturen

This is normal Dutch word order.

Compare:

• Ik probeer het boek te lezen.
• Zij komt hier om koffie te drinken.
• Hij belt om een afspraak te maken.

In all of these, the main infinitive comes near the end.

Sturen by itself usually means to send in a broad sense, but also to steer depending on context.

Opsturen is more specific and often means:

• to send off
• to send in
• to mail
• to submit by sending

So in a sentence about a contract, opsturen sounds very natural because it suggests sending the document onward to someone.

Yes, that is grammatically possible, but it sounds a bit different in emphasis.

Compare:

• Op kantoor gebruik ik een scanner ...
  Emphasis on where this happens.

• Ik gebruik op kantoor een scanner ...
  More neutral start with I, though the placement of op kantoor inside the sentence can sound slightly more marked depending on context.

The version you were given is very natural because it foregrounds the location.

Because only the finite verb in the main clause follows the V2 rule.

Main clause:

• Op kantoor gebruik ik een scanner

Here, gebruik is the finite verb and must be in second position.

But the second part is an infinitive clause with om ... te:

• om het contract op te sturen

That part does not follow the same V2 rule because it is not a full main clause.

Yes. A very useful related sentence is:

• Ik stuur het contract op. = I send the contract off.

Notice how the separable verb behaves:

• infinitive: opsturen
• main clause: stuur ... op
• with te: op te sturen
• past participle: opgestuurd

Learning all four patterns together is a great way to master separable verbs.

Yes. Scanner is a normal Dutch noun, borrowed from English.

Dutch uses many international or English-based technology words, for example:

• de scanner
• de computer
• de printer

Even when a word looks familiar, you still need to learn how it behaves in Dutch grammar, especially its article and plural form.