Sy het die leerlingbestuurder ratte hoor wissel.

Here Sy means she.

Afrikaans sy can also mean his in other sentences, but in this sentence it is followed by the verb het, so it is clearly a subject pronoun: She has / she did. The capital letter does not help much here, because it is only capitalized for being at the start of the sentence.

Afrikaans very often uses the perfect form where English uses a simple past.

So:

• Sy het ... gehoor / hoor ... = She heard ...

In everyday Afrikaans, het is the normal way to talk about many completed past actions. So even though English says she heard, Afrikaans naturally says sy het.

That is because of a common Afrikaans pattern with verbs like hoor and sien when they are followed by another infinitive.

Normally, after het, you expect a past participle:

• Ek het hom gehoor = I heard him

But when hoor is followed by another verb, Afrikaans usually keeps hoor as an infinitive:

• Ek het hom hoor sing = I heard him sing
• Sy het die leerlingbestuurder ratte hoor wissel = She heard the learner driver change gears

So this is a kind of double infinitive construction: hoor wissel, not gehoor gewissel.

Because after a verb of perception like hoor, Afrikaans uses a bare infinitive.

So you say:

• Ek hoor hom praat = I hear him talk
• Ek het hom hoor praat = I heard him talk

Not:

• Ek hoor hom te praat ❌

So hoor wissel is exactly what you expect here.

Because Afrikaans often sends the non-finite verbs to the end of the clause.

The structure is roughly:

• Sy = subject
• het = finite auxiliary
• die leerlingbestuurder ratte = the noun phrases in the middle
• hoor wissel = the final verb cluster

So the sentence ends with the verbs:

• Sy het die leerlingbestuurder ratte hoor wissel

This is normal Afrikaans word order.

Because in Afrikaans, objects often appear before the final verb cluster.

In English, you might expect something like:

• She heard the learner driver change gears

In Afrikaans, the object of wissel is placed before the verbs at the end:

• ... ratte hoor wissel

So ratte belongs with wissel, even though it stands before it.

The one doing the gear-changing is die leerlingbestuurder.

So the meaning is:

• She heard [the learner driver] [change gears].

A useful comparison is:

• Ek het hom sien hardloop = I saw him run

In that kind of pattern, the noun or pronoun before the second verb is understood as the doer of that second verb.

Here:

• die leerlingbestuurder = the one who is changing gears
• ratte = the thing being changed

It means learner driver.

Afrikaans, like Dutch and German, very often forms nouns by writing them together as one compound word:

• leerling = learner / pupil
• bestuurder = driver
• leerlingbestuurder = learner driver

So yes, it is normal that it is written as a single word.

Yes, here ratte means gears.

Afrikaans rat can mean:

• rat the animal
• gear / cog in a mechanical context

In driving language, ratte wissel means change gears or shift gears. The context makes it clear that this is not about animals.

Because ratte is being used in a more general, non-specific way, like English change gears.

Compare:

• ratte wissel = change gears in general
• die ratte wissel = change the gears / change those specific gears

So the sentence is talking about the action of gear-changing, not about some particular set of gears already identified in the conversation.

These two sentences are close in English, but the Afrikaans structures suggest different things.

Sy het die leerlingbestuurder ratte hoor wissel
means she physically heard the learner driver changing gears. It is a direct perception construction.

Sy het gehoor dat die leerlingbestuurder ratte wissel
means she heard that the learner driver changes/is changing gears. This can mean she was told about it or learned it indirectly.

So:

• hoor + infinitive = direct hearing of an action
• gehoor dat ... = hearing information or a report