By die poskantoor groet die posbode my en neem my brief.

Here by means at.

So by die poskantoor = at the post office.

Afrikaans often lets you put a place or time phrase first if you want to set the scene. That is what happens here:

• By die poskantoor = at the post office
• then the rest of the sentence follows

So this sentence starts by telling you where the action happens.

This is a very common Afrikaans word-order pattern.

In a main clause, the finite verb usually comes in the second position. This is often called the V2 rule.

Here, the first position is taken by By die poskantoor. Because that whole phrase is in first position, the verb must come next:

• By die poskantoor = first position
• groet = second position
• die posbode = subject comes after the verb

So:

• By die poskantoor groet die posbode my.

If you started with the subject instead, you could also say:

• Die posbode groet my by die poskantoor.

Both are grammatical, but the focus is slightly different.

Die means the.

Afrikaans uses die as the definite article for:

• singular nouns
• plural nouns
• all genders

So unlike languages such as German or Dutch, Afrikaans does not change the article for masculine, feminine, or neuter nouns.

In this sentence:

• die poskantoor = the post office
• die posbode = the postman / mail carrier

It appears twice because both nouns are definite.

Afrikaans very often writes compound nouns as one word.

So:

• pos
  • kantoor → poskantoor
• pos
  • bode → posbode

This is similar to how German handles compounds, and Afrikaans does this much more than English.

Meanings:

• poskantoor = post office
• posbode = postman / postal worker / mail carrier

Yes, historically that is basically the idea.

• pos = post / mail
• bode = messenger

Together, posbode means the person who delivers or handles mail, usually translated as:

• postman
• mail carrier
• postal worker

Depending on context, English may choose a more gender-neutral translation such as mail carrier.

Yes. In Afrikaans, my can mean both:

• me as an object pronoun
• my as a possessive

In this sentence:

• groet die posbode my = the postman greets me
• neem my brief = takes my letter

So the same word form is used for two different jobs.

Compare:

• Ek = I
• my = me / my

Context usually makes the meaning clear.

Because possessives normally replace the article.

Just like in English, you say:

• my letter not
• the my letter

So in Afrikaans:

• my brief = my letter

You would not normally say die my brief.

Yes. In Afrikaans, brief as a noun means letter.

So:

• ’n brief = a letter
• my brief = my letter

This is a false friend for English speakers, because English brief is usually an adjective meaning short. In Afrikaans, brief here is definitely the noun letter.

The subject does not need to be repeated because it is understood to be the same subject: die posbode.

So the sentence means:

• the postman greets me and takes my letter

Afrikaans, like English, often leaves the subject out of the second coordinated part when it is the same:

• Die posbode groet my en neem my brief.
• The subject for both verbs is die posbode.

In your sentence, the place phrase is first, but the idea is the same:

• By die poskantoor groet die posbode my en neem my brief.

Yes, that is also correct.

The difference is mainly in emphasis:

• By die poskantoor groet die posbode my en neem my brief.
  Emphasis first on where it happens.

• Die posbode groet my en neem my brief by die poskantoor.
  More neutral, starting with the subject.

Afrikaans allows this kind of movement, but when something other than the subject comes first, remember that the verb still stays in second position.

It can mean both, depending on context.

Groet commonly means:

• greet
• say hello to
• sometimes send regards to, in other contexts

In this sentence, groet die posbode my means:

• the postman greets me or more naturally in English:
• the postman says hello to me