Because Afrikaans uses die as the definite article the, and it does not change for gender or number in normal use.
So:
Unlike languages such as German or Dutch, Afrikaans does not have different forms like der / die / das or complicated case endings here. One simple form, die, is used for both nouns.
Because Afrikaans, like English, can use a structure like:
So:
The adjective helder comes after die kamer because it describes the result for that object.
Compare the English pattern:
Because helder is being used predicatively, not directly before the noun.
Compare these two uses:
So in your sentence, helder is correct because it is not placed directly in front of kamer.
It is best understood as an adjective.
It describes the state of die kamer:
So even though it comes after the object, it is still linked to kamer, not to the verb in the way an adverb would be.
A helpful test is this:
Yes, you could, but it is not exactly the same structure.
The first version focuses more directly on the action of lighting.
The second focuses on the result: the room becomes bright.
So both are natural, but maak ... helder specifically highlights the change in the room’s brightness.
A rough English-style guide would be:
dee lamp mahk dee KAH-mer HEL-der
A few notes:
Pronunciation can vary a bit by speaker and region, but that guide will get you close.
You would normally use the Afrikaans double negative:
Die lamp maak nie die kamer helder nie.
That literally looks like:
The lamp makes not the room bright not
But in normal English, it means:
The lamp does not make the room bright.
This is a very important Afrikaans pattern: in most ordinary negative sentences, you use nie ... nie.
Afrikaans follows a verb-second pattern in main clauses. That means if you move another element to the front, the verb usually comes right after it.
For example:
Notice that maak stays in second position after Vandag.
This is a useful thing to know, because the basic sentence you were given is simple, but Afrikaans word order becomes much easier once you recognize this pattern.