Ek het die leerlingbestuurder stadig hoor rem.

Because Afrikaans often uses a double infinitive after het when verbs like hoor, sien, laat, help, and modal verbs are followed by another verb.

So in this sentence, hoor stays as hoor, and the second verb rem also stays in the infinitive:

Ek het die leerlingbestuurder stadig hoor rem.

But if hoor is used on its own, then the normal past participle is gehoor:

Ek het 'n vreemde geluid gehoor. = I heard a strange sound.

So:

• with another verb → hoor rem
• without another verb → gehoor

Because the sentence contains:

• the auxiliary verb het
• the perception verb hoor
• the main action verb rem

In Afrikaans perfect tense, het comes near the beginning, and the non-finite verbs usually go to the end. Here the final verb cluster is hoor rem.

So the structure is roughly:

• Ek = subject
• het = auxiliary
• die leerlingbestuurder = object
• stadig = adverb
• hoor rem = verb cluster at the end

This is a very normal Afrikaans pattern.

After verbs like hoor and sien, Afrikaans normally uses a bare infinitive, without te.

So you get:

• Ek hoor hom sing.
• Ek sien haar hardloop.
• Ek het die leerlingbestuurder hoor rem.

Not:

• Ek het die leerlingbestuurder hoor te rem.

That would sound ungrammatical.

Leerlingbestuurder is a compound noun:

• leerling = learner / pupil
• bestuurder = driver

Together, leerlingbestuurder means learner driver.

Afrikaans, like Dutch and German, often writes compound nouns as one word. So where English writes learner driver, Afrikaans normally writes leerlingbestuurder.

Die is the definite article, meaning the.

So:

die leerlingbestuurder = the learner driver

A useful thing for English speakers is that Afrikaans does not change the article for gender. You use die for all genders.

Here it most naturally means that the learner driver braked slowly.

So stadig is describing rem.

That is the natural interpretation of the sentence:

Ek het die leerlingbestuurder stadig hoor rem.
= I heard the learner driver brake slowly.

In other words, stadig tells you how the braking happened, not how the hearing happened.

Yes. Here rem is a verb meaning to brake.

It is in the infinitive form because it follows hoor in this construction.

So in this sentence:

• hoor = to hear
• rem = to brake

Afrikaans also has rem as a noun in other contexts, meaning brake, but not here.

It is the person that was heard, so it functions as the object of hoor.

At the same time, it is also the one doing the braking, so it is the logical subject of rem.

English works similarly:

I heard the learner driver brake.

In that English sentence, the learner driver is both:

• the one I heard
• the one who did the braking

The Afrikaans sentence works the same way.

Yes, that is also possible, but it is a slightly different structure.

• Ek het die leerlingbestuurder stadig hoor rem
• Ek het gehoor hoe die leerlingbestuurder stadig rem

Both can express roughly the same idea.

The first version is more compact and uses the double infinitive pattern.
The second version uses gehoor plus a clause with hoe.

So for learners, it is useful to recognize that Afrikaans can express this idea in more than one natural way.