Is daar iemand by die deur, of hoor ek iets in die straat?

Because Afrikaans usually forms a yes/no question by putting the finite verb first.

• Statement: Daar is iemand by die deur.
• Question: Is daar iemand by die deur?

So Is daar iemand ...? works like English Is there someone ...?

In this sentence, both parts are questions:

• Is daar iemand by die deur
• hoor ek iets in die straat

That is why the verbs is and hoor come before the subjects.

Here daar does not mean a literal there in the sense of location. It is the existential daar, used in sentences like:

• Daar is 'n probleem. = There is a problem.
• Daar was mense buite. = There were people outside.

So Is daar iemand by die deur? means Is there anyone at the door?

Afrikaans uses daar very much like English uses there in there is / there are.

Iemand already means someone / anyone, so it does not need an article.

• iemand = someone / anyone
• iets = something / anything

In questions, these words often have the broader any- sense in English:

• Is daar iemand ...? = Is there anyone ...?
• hoor ek iets ...? = do I hear anything ...?

So no extra word like 'n is needed before iemand.

They are both indefinite pronouns, but they refer to different kinds of things:

• iemand = someone / anyone → a person
• iets = something / anything → a thing / sound / event

In the sentence:

• iemand by die deur = a person at the door
• iets in die straat = something in the street

So the speaker is wondering whether the noise is caused by a person at the door or something in the street.

These are just the prepositions that fit the meaning:

• by die deur = at the door / by the door
• in die straat = in the street

By often means at, near, or by.
So iemand by die deur means someone is at the door area, not literally inside the door.

In die straat means the sound seems to be coming from the street.

English and Afrikaans prepositions often match, but not always, so it is good to learn them as part of a phrase:

• by die deur
• in die straat

Because this clause is also a question.

Afrikaans question word order usually puts the verb before the subject:

• Statement: Ek hoor iets in die straat.
• Question: Hoor ek iets in die straat?

Even after of = or, the second part keeps question word order because it is still a question:

• Is daar iemand by die deur, of hoor ek iets in die straat?

So this is basically:

• Is there someone at the door, or am I hearing something in the street?

Yes. In this sentence, of means or.

It links two alternatives:

• maybe there is someone at the door
• or maybe the speaker hears something in the street

Be careful, though: of can also mean whether / if in some contexts, depending on the sentence. But here it is clearly the ordinary or joining two possibilities.

Yes, here die means the in both places:

• die deur = the door
• die straat = the street

A useful thing for learners is that Afrikaans die does not change for gender or number the way articles do in some languages. It is the standard definite article for:

• singular nouns
• plural nouns
• all genders

So:

• die deur = the door
• die deure = the doors
• die man = the man
• die vrou = the woman

If you remove the question word order, you get the statement forms:

• Daar is iemand by die deur.
• Ek hoor iets in die straat.

The question sentence combines them as possibilities:

• Is daar iemand by die deur, of hoor ek iets in die straat?

This is a good way to study Afrikaans word order: compare statement and question versions side by side.

Mostly yes. Straat means street.

In in die straat, it refers to the street outside. Depending on context, English might say:

• in the street
• out in the street
• sometimes even on the street

Afrikaans uses in die straat naturally here to mean the noise is coming from the street area.

Yes, it sounds natural. It has a very everyday, conversational feel.

A speaker might say this when they hear a noise and are unsure where it comes from:

• maybe from someone at the door
• maybe from outside in the street

It is also a useful example because it shows several very common Afrikaans patterns at once:

• Is daar ...? for Is there ...?
• verb-first question order
• iemand and iets
• common prepositions like by and in