My broer stryk sy broek, maar sy suster bêre reeds die handdoeke in die kas.

Yes. My is the Afrikaans possessive my. It is capitalized here only because it is the first word of the sentence.

• my broer = my brother
• In the middle of a sentence, it would normally be written my, not My.

Like English, the possessive comes before the noun.

In this sentence, both instances of sy mean his.

• sy broek = his trousers/pants
• sy suster = his sister

They both refer back to my brother.

A useful thing to know is that sy can also mean she when it is used as a subject pronoun:

• Sy stryk. = She is ironing.
• sy broek = his trousers

So the function depends on where it appears in the sentence.

Because Afrikaans verbs usually do not conjugate in the present tense the way English verbs do.

You use the same basic verb form with different subjects:

• Ek stryk
• Jy stryk
• Hy stryk
• Ons stryk

The same is true for bêre.

This is one of the simpler parts of Afrikaans grammar for English speakers: there is no extra -s like in English he irons.

In Afrikaans, broek is normally singular for one item of clothing.

So:

• sy broek = his trousers / his pants

If you mean more than one pair, you can use the plural broeke.

This is different from English, where pants and trousers are usually plural in form even when referring to one garment.

Here, stryk means to iron clothes.

Because the object is sy broek, the meaning is clearly about ironing clothing.

The verb stryk can have other meanings in other contexts, such as to smooth or to stroke, but in this sentence the clothing meaning is the natural one.

Bêre means something like put away, store, or tidy away.

So bêre die handdoeke in die kas suggests putting the towels in their proper place, not just moving them somewhere randomly.

The circumflex in ê is part of the standard spelling. You should try to include it when writing the word.

Reeds means already.

So:

• sy suster bêre reeds die handdoeke = his sister is already putting away the towels

Reeds is perfectly correct, but it can sound a bit more formal or written than al, which is also very common in everyday Afrikaans.

For example, many speakers would also say:

• sy suster bêre al die handdoeke in die kas

Yes. Die is the definite article for both singular and plural nouns in Afrikaans.

So:

• die kas = the cupboard
• die handdoeke = the towels

Afrikaans does not change the depending on gender or number.

Also, handdoeke is the plural of handdoek.

Afrikaans often uses the simple present tense where English would use the present progressive.

So:

• My broer stryk sy broek can mean My brother irons his trousers or My brother is ironing his trousers
• sy suster bêre reeds die handdoeke can mean his sister already puts away the towels or is already putting away the towels

Context tells you which meaning is intended.

Afrikaans can express an ongoing action more explicitly with a structure like is besig om te, but that is not necessary here.

Because after maar you get another main clause, and in a normal Afrikaans main clause the finite verb usually comes second.

So the pattern here is:

• sy suster = subject
• bêre = finite verb
• reeds = adverb
• die handdoeke = object
• in die kas = prepositional phrase

This is very typical Afrikaans word order.

A helpful rule is: in ordinary main clauses, the verb likes to stay in the second position.