My ouma sê dat my neef slim is, maar my nig sê sy kan net so goed kook.

ouma means grandma or granny. It is a very common everyday family word, not unusually childish or rude.

A more formal word would be grootmoeder, but in normal speech ouma is much more natural.

sê is the Afrikaans verb to say.

The ê marks the vowel sound in spelling. You do not need to memorize a complicated rule here yet; the important thing is simply that sê is the normal written form of the verb. It is pronounced roughly like seh, with a longer/opener vowel than a plain e.

Yes. In Afrikaans, slim is a false friend for English speakers.

In Afrikaans, slim usually means clever, intelligent, or smart. It does not normally mean thin the way it does in English.

So:

• Hy is slim = He is clever
• not He is thin

For thin, Afrikaans would more likely use words like maer or skraal, depending on context.

Traditionally, yes:

• neef = male cousin or nephew
• nig = female cousin or niece

So these words can refer either to cousins or to a sibling’s child, depending on context.

In this sentence, they clearly mean male cousin and female cousin.

A native English speaker may notice that nig looks strange because of English, but in Afrikaans it is simply a normal kinship word with a completely different meaning.

dat means that.

It introduces a subordinate clause, just like English that in:

• My grandma says that my cousin is smart

So:

• My ouma sê dat my neef slim is

literally works like:

• My grandma says that my male cousin smart is

except Afrikaans changes the word order inside that subordinate clause.

Because after dat, Afrikaans normally uses subordinate-clause word order, where the finite verb goes to the end.

Compare:

• Main clause: My neef is slim = My cousin is smart
• Subordinate clause: dat my neef slim is = that my cousin is smart

This is one of the big word-order differences between English and Afrikaans.

After verbs like sê (say), Afrikaans very often leaves out dat.

So both of these are possible:

• my nig sê dat sy net so goed kan kook
• my nig sê sy kan net so goed kook

The version without dat is very common and natural.

A useful thing to notice is this:

• with dat, you expect subordinate-clause order
• without dat, the clause often keeps normal main-clause order

That is why sy kan ... looks more straightforward than dat my neef slim is.

Yes, here sy means she.

That can be confusing, because sy can also mean his in other sentences. The job it is doing in the sentence tells you which meaning it has.

Here it comes before kan and acts as the subject of the clause:

• sy kan ... kook = she can ... cook

So in this sentence, it is definitely she.

net so goed means just as well or equally well.

A very literal breakdown is:

• net = just
• so = so
• goed = good / well

Afrikaans often uses goed where English would use well. In other words, goed can work adverbially in many everyday contexts.

So:

• Sy kook goed = She cooks well
• Sy kan net so goed kook = She can cook just as well

Because kan is a modal verb, meaning can, and modal verbs in Afrikaans are followed by another verb in the infinitive.

That second verb often comes later in the clause, usually at the end:

• Sy kan kook = She can cook
• Sy kan net so goed kook = She can cook just as well

So kan carries the tense, and kook stays in its basic verb form.

maar means but.

It joins two main clauses:

• My ouma sê dat my neef slim is
• maar my nig sê sy kan net so goed kook

Unlike dat, maar does not force subordinate-clause word order. It simply connects one statement to another, so the clause after maar keeps normal main-clause structure.