Die kat slaap onder die bank.

Because die is the normal definite article in Afrikaans, meaning the. Afrikaans does not change the for gender, case, or most noun classes, so you use die for both the cat and the bench/sofa.

• die kat = the cat
• die bank = the bench / sofa / couch / bank depending on context

So the sentence literally follows the same pattern as English:

• The cat sleeps under the bench/sofa.

It serves a similar job, but Afrikaans is much simpler. Unlike Dutch or German, Afrikaans does not keep multiple forms of the definite article.

So instead of learning several versions of the, you mostly just use:

• die = the

That simplicity is one of the nice features of Afrikaans for English speakers.

Afrikaans verbs are much less inflected than English verbs. The verb usually stays the same no matter who the subject is.

So:

• Ek slaap = I sleep / I am sleeping
• Jy slaap = you sleep / you are sleeping
• Die kat slaap = the cat sleeps / the cat is sleeping

Afrikaans often uses the simple present where English may use either sleeps or is sleeping, depending on context.

Yes. This is standard Afrikaans main-clause word order:

Subject + verb + place phrase

• Die kat = subject
• slaap = verb
• onder die bank = prepositional phrase showing location

So the structure is very natural and close to English:

• The cat sleeps under the bank/sofa.

Yes. Onder means under / beneath, and it works very much like English under.

Examples:

• onder die tafel = under the table
• onder die bed = under the bed
• onder die bank = under the sofa / bench

It is a preposition, so it comes before the noun phrase.

Bank can mean different things depending on context. In everyday Afrikaans, it can mean:

• sofa / couch
• bench
• sometimes bank in the financial sense, depending on context

In a sentence about a cat sleeping under it, sofa/couch or bench are the most likely meanings. If you were already shown the meaning, that context decides which one fits best.

In Afrikaans, common nouns are not capitalized unless they start a sentence. So:

• kat = cat
• bank = sofa / bench
• huis = house

Only the first word of the sentence is capitalized here because it begins the sentence:

• Die kat slaap onder die bank.

This is different from German, where all nouns are capitalized.

A simple English-friendly guide is:

• Die ≈ dee
• kat ≈ kut/cat with a short a
• slaap ≈ slahp
• onder ≈ ON-der
• die ≈ dee
• bank ≈ bahnk

A rough full pronunciation: dee kaht slahp ON-der dee bahnk

A few notes:

• aa in slaap is a long vowel.
• a in kat is shorter.
• Afrikaans pronunciation is generally quite consistent once you learn the spelling patterns.

Yes. They are clearly related cognates.

• English: cat
• Afrikaans: kat

This is common in Afrikaans: many basic words look familiar to English speakers, although spelling and pronunciation may differ.

Yes. In many contexts, Afrikaans simple present can match either English simple present or present continuous.

So Die kat slaap onder die bank can mean:

• The cat sleeps under the couch or
• The cat is sleeping under the couch

The surrounding context usually makes it clear which English translation sounds best.

Afrikaans normally uses a double negative with nie ... nie.

So:

• Die kat slaap onder die bank. = The cat sleeps under the couch.
• Die kat slaap nie onder die bank nie. = The cat is not sleeping under the couch.

This double nie pattern is very important in Afrikaans.

Usually, yes. That is one of the easiest parts of Afrikaans grammar.

Examples:

• Ek slaap onder die bank. = I sleep under the couch.
• Die hond slaap onder die bank. = The dog sleeps under the couch.
• Ons slaap onder die bank. = We sleep under the couch.

The verb slaap stays the same. Afrikaans does not usually add endings like English sleep/sleeps.