Die velling en remkussing is vuil.

Yes. Die is the normal definite article in Afrikaans, so here it means the.

A useful thing for English speakers to know is that Afrikaans does not change the article for gender the way languages like German do. Die is used for:

• masculine nouns
• feminine nouns
• neuter nouns
• singular nouns
• plural nouns

So die velling and die remkussing both simply use die.

Afrikaans often lets one article cover both nouns when they are joined by en.

So Die velling en remkussing means that both nouns belong under the same the:

• the rim and brake pad

You can also repeat it:

• Die velling en die remkussing is vuil.

That version is also grammatical, but repeating die sounds a bit more explicit or slightly more emphatic. Using it once is very natural.

Because in Afrikaans, the present tense of wees (to be) is is for all persons and numbers.

So Afrikaans says:

• Ek is — I am
• Jy is — you are
• Hy is — he is
• Ons is — we are
• Hulle is — they are

So even with a subject like Die velling en remkussing that refers to two things, Afrikaans still uses is, not a separate plural form like English are.

En means and. It joins the two nouns:

• velling
• remkussing

Together they form a compound subject: Die velling en remkussing.

Because Afrikaans, like Dutch and German, very often writes compound nouns as a single word.

Here:

• rem = brake
• kussing = cushion/pad

So remkussing is a compound noun meaning brake pad.

This is very normal in Afrikaans. English sometimes uses two words where Afrikaans prefers one.

Because vuil is being used predicatively here — in other words, after the verb is.

In Afrikaans, adjectives used after a linking verb usually stay in their basic form:

• Die remkussing is vuil.
• Die velling is vuil.

So vuil does not need an ending here.

This is different from adjectives placed before a noun, where Afrikaans often adds -e:

• die vuil remkussing
• die vuil velling

So:

• after is → vuil
• before a noun → often vuil still looks the same here, but many adjectives would take -e

Yes. This sentence follows a very familiar main-clause pattern:

• Subject: Die velling en remkussing
• Verb: is
• Complement: vuil

So it works much like English:

• The rim and brake pad are dirty.

For a simple statement like this, the structure is very straightforward for an English speaker.

Not in the way you would in languages like German or French.

For this sentence, you do not need to learn separate words for the based on gender. Afrikaans has greatly reduced grammatical gender, and die works perfectly here regardless of whether the noun would historically have been masculine, feminine, or neuter.

That makes sentences like this much simpler to build.

It describes both nouns.

Because Die velling en remkussing is one joined subject, the adjective after is applies to the whole subject. So the sentence means that both items are dirty.

If you wanted to make that especially clear in English-style thinking, you could understand it as:

• The rim and the brake pad are dirty.

You could, but it would make a different structure.

Your original sentence:

• Die velling en remkussing is vuil. means that the speaker is stating the condition of those items.

If you put the adjective before the noun, you are turning it into part of the noun phrase:

• die vuil velling
• die vuil remkussing

That is more like saying:

• the dirty rim
• the dirty brake pad

So the original sentence is the natural way to say that those items are dirty right now.

Yes, that is also correct.

The difference is mostly stylistic:

• Die velling en remkussing is vuil → compact, natural
• Die velling en die remkussing is vuil → more explicit, with each noun individually marked

Both are good Afrikaans.