You usually use the Afrikaans double negative:
A simple way to think about it is:
This double-nie pattern is very common in standard Afrikaans.
For a yes/no question, you usually put the verb first:
This is similar to English Is the candle small?
So the statement:
becomes the question:
You would use the indefinite article 'n:
'n Kers is klein.
A very important writing point:
So you write:
not: