Die kinders bou ’n huis van sand naby die golwe.

’n is the Afrikaans indefinite article, equivalent to a or an in English. It always precedes a noun to mark it as non-specific. In writing, it is shown with an apostrophe at the front ( ’ ) because an a has been dropped from the older form een.

die is the definite article in Afrikaans, equivalent to the in English.

• You use die before a plural or singular noun when you refer to something specific or already known.
• Here die kinders means the children, and die golwe means the waves.

Use die when you have a specific thing in mind or when you have mentioned it before. Use ’n when you introduce something new or non-specific.
Examples:

• Ek sien die hond → I see the dog (a particular dog).
• Ek sien ’n hond → I see a dog (just any dog).

Afrikaans generally does not use a separate continuous aspect for main verbs.

• Die kinders bou ’n huis can mean either “The children build a house” or “The children are building a house,” depending on context.
• If you want to emphasise that the action is ongoing right now, you can say Die kinders is besig om ’n huis te bou.

Here van means of or from, indicating the material something is made of. In English you might say a house of sand or a sand house.

• huis van sand literally house of sand.
• You cannot drop van if you want to express material.

uit often means out of or made out of, but in Afrikaans material is normally expressed with van.

• ’n tafel van hout (a table of/from wood) is correct.
• ’n tafel uit hout is less common and may sound odd.

naby is a preposition meaning near or close to. It always takes a noun phrase with an article:

• naby die golwe = near the waves
  You could also use by for by the waves, but naby stresses proximity.

golwe is the plural form of golf (wave). We use the plural because beaches usually have many waves. Plurals in Afrikaans typically add –e or –s, here golf → golwe.

sand is an uncountable noun in Afrikaans, just like in English. Uncountable nouns do not take plural endings and are used the same in singular and “plural” contexts.

You can, but it shifts emphasis. The normal order is Subject–Verb–Object–Location:

• Die kinders bou ’n huis van sand naby die golwe.
  If you start with the location, you emphasise where it happens:
• Naby die golwe bou die kinders ’n huis van sand.
  Both are grammatically correct, but the first is more neutral.