Die argitek handig die bouplan in.

Because Afrikaans uses die as the definite article the.

So the sentence has two noun phrases:

• die argitek = the architect
• die bouplan = the building plan / blueprint

Each noun phrase gets its own article, just like in English if you say the architect hands in the plan.

A useful thing to remember: Afrikaans die does not change for gender, and it is also used for plural nouns.

Yes. The full verb is inhandig, meaning to hand in / submit.

In a main clause, many Afrikaans verbs with a separable first part split apart:

• inhandig → handig ... in

So:

• Die argitek handig die bouplan in.

This is similar to English hand in in The architect hands the plan in.

The in here is not just an ordinary preposition by itself. It is a verb particle, part of the separable verb inhandig.

Because in an ordinary statement, Afrikaans usually puts the finite verb in the second position.

With a separable verb, the conjugated verb stem goes to second position, and the particle goes to the end:

• Die argitek | handig | die bouplan | in

So inhandig gets split in this sentence.

You would normally only see it written together in forms such as:

• dat die argitek die bouplan inhandig
• Die argitek het die bouplan ingehandig

Usually, no. Afrikaans verbs are much simpler than English verbs in this way.

In the present tense, the verb normally stays the same regardless of the subject:

• ek handig in
• jy handig in
• hy handig in
• ons handig in
• hulle handig in

So Afrikaans does not have the same kind of I hand / he hands difference that English has.

Bouplan is a compound noun:

• bou = build / building
• plan = plan

Together, bouplan means building plan, often something like a blueprint or architectural plan depending on context.

Afrikaans forms compound nouns very freely, and they are usually written as one word. That is why it is bouplan, not bou plan.

No. Argitek is not marked for grammatical gender in the way nouns are in some other languages.

Afrikaans does not have grammatical gender like masculine/feminine/neuter articles. The article stays die.

So die argitek can mean:

• the male architect
• the female architect
• simply the architect, without saying anything about gender

If you need to make gender explicit, you normally do that with extra words, not by changing the noun itself.

This is a very useful question, because separable verbs change shape depending on the structure.

Main clause:

• Die argitek handig die bouplan in.

Yes/no question:

• Handig die argitek die bouplan in?

Subordinate clause:

• ... dat die argitek die bouplan inhandig.

Perfect tense:

• Die argitek het die bouplan ingehandig.

Infinitive with te:

• om die bouplan in te handig

So the dictionary form is inhandig, but in a simple main clause it often splits.

Afrikaans normally uses a double negative with nie ... nie.

So:

• Die argitek handig nie die bouplan in nie.

That is the standard neutral negation: The architect does not hand in the building plan.

Notice that with a separable verb, the particle in still stays near the end, before the final nie.

Here it is something else: it is a verbal particle.

That matters because it is part of the verb inhandig, not a separate phrase like in the office or in the box.

Compare:

• Die argitek handig die bouplan in.
  Here in belongs to the verb inhandig.

Versus a real preposition:

• Die bouplan is in die kantoor.
  Here in means in and introduces a location phrase.

So in your sentence, in does not mean location. It helps form the verb meaning submit / hand in.

In this sentence, die is usually pronounced roughly like dee.

That can be surprising for English speakers, because it is spelled like the English word die, but it does not sound the same.

So:

• die argitek ≈ dee ar-gi-tek

That is one of the first pronunciation points learners usually need to remember.