Ons het die motor by die voetoorgang sien stop.

In Afrikaans, the perfect form is very often used where English would simply use the simple past.

So:

Ons het die motor ... sien stop
means
We saw the car ... stop

Literally, Afrikaans is using a form with het, but in normal English translation you usually just use saw, not have seen.

Because sien is followed by another verb, stop.

Afrikaans has a common pattern where certain verbs, especially verbs like sien, hoor, laat, and modal verbs, stay in the infinitive form after het when they are followed by another infinitive.

So you get:

Ons het die motor sien stop
not normally
Ons het die motor gesien stop

But if sien stands alone, then you do use gesien:

Ons het die motor gesien = We saw the car

Because the sentence means we saw the car stop.

The two verbs work together:

• sien = see
• stop = stop

So the structure is basically:

Ons het + die motor + by die voetoorgang + sien stop

Afrikaans often puts the non-finite verbs near the end of the clause. Here, sien stop acts like a little verb group meaning saw it stop.

Because sien is the perception verb, and stop is the action that was perceived.

So:

• sien stop = see stop = see something stop

This is similar to English:

We saw the car stop

You do not say:

We saw the car see

So the order reflects the meaning: first the act of perceiving, then the action perceived.

After sien, Afrikaans uses a bare infinitive.

So:

die motor sien stop = see the car stop

Not:

die motor sien te stop

This is very close to English, where you also say:

We saw the car stop

not

We saw the car to stop

It means at the pedestrian crossing, by the crosswalk, or near the crosswalk, depending on context.

Here by is a location word. It often means:

• at
• by
• near

So by die voetoorgang tells you where the car stopped.

It is a compound noun:

• voet = foot
• oorgang = crossing / passage

So voetoorgang is literally something like foot-crossing, and idiomatically it means pedestrian crossing or crosswalk.

Afrikaans very often joins nouns into one word like this.

Because die is the normal definite article in Afrikaans.

It can mean the for:

• singular nouns
• plural nouns
• any grammatical gender

So:

• die motor = the car
• die voetoorgang = the pedestrian crossing

Afrikaans does not have different words like the for masculine, feminine, and neuter nouns.

Yes, Afrikaans allows some flexibility.

For example, you could also say:

Ons het die motor sien stop by die voetoorgang.

That still means the same basic thing.

The version you were given keeps the location phrase before the final verb group, which is very normal in Afrikaans. Moving it can slightly change what gets emphasis, but the meaning stays very similar.

Yes. In everyday Afrikaans, motor commonly means car or automobile.

So:

die motor = the car

Even though English motor often means an engine or a general mechanical motor, Afrikaans motor is very commonly the ordinary word for a car.