Die munisipaliteit gaan die bouplan jaarliks na.

Here, gaan ... na is the separable verb nagaan.

nagaan means things like:

• to check
• to examine
• to review
• to go over

So this is not the ordinary verb gaan meaning to go. The whole idea is review/check.

Because nagaan is a separable verb in Afrikaans.

In a normal main clause, the first part stays in the usual verb position, and the particle moves to the end:

• Die munisipaliteit gaan die bouplan jaarliks na.

Compare that with the infinitive form, where it stays together:

• Die munisipaliteit moet die bouplan jaarliks nagaan.

So the final na is not random. It belongs to the verb.

No. In this sentence, gaan is part of nagaan, not a future marker.

That is an important distinction:

• Die munisipaliteit gaan die bouplan jaarliks na.
  = The municipality reviews/checks the building plan annually.

• Die munisipaliteit gaan die bouplan jaarliks nagaan.
  = The municipality is going to review/check the building plan annually.

So the final na tells you that this is the separable verb nagaan, not future gaan + infinitive.

Look for nagaan.

That is the dictionary form. In actual sentences, it may appear split apart, as in:

• gaan ... na

So if you only look up gaan, you may miss the real meaning of the sentence.

Because die is the definite article in Afrikaans for the.

Here it appears before both nouns:

• die munisipaliteit = the municipality
• die bouplan = the building plan

Afrikaans does not have different definite articles for grammatical gender the way some other languages do. die is very common and covers a lot of ground.

Afrikaans very often writes compound nouns as one word.

So:

• bou = build / building
• plan = plan

Together:

• bouplan = building plan

This is extremely normal in Afrikaans. English often writes similar expressions as two words, but Afrikaans usually joins them.

jaarliks means annually or yearly.

Yes, elke jaar is also possible:

• Die munisipaliteit gaan die bouplan elke jaar na.

The difference is mostly style:

• jaarliks sounds a bit more compact and often a bit more formal
• elke jaar is very natural and everyday

Both are correct.

Because Afrikaans verbs usually do not change according to person or number in the present tense.

So you get:

• ek gaan
• jy gaan
• die munisipaliteit gaan
• hulle gaan

This is much simpler than English, where you have I go but he goes.

The sentence follows a very common Afrikaans pattern:

subject + finite verb + object + adverb + separable particle

So here you have:

• Die munisipaliteit = subject
• gaan = finite verb
• die bouplan = object
• jaarliks = adverb
• na = separable particle

That is why the sentence looks the way it does.

Yes, adverbs can often move, but some positions sound more neutral than others.

The original sentence is very natural:

• Die munisipaliteit gaan die bouplan jaarliks na.

You can also front jaarliks for emphasis:

• Jaarliks gaan die munisipaliteit die bouplan na.

That still follows the Afrikaans rule that the finite verb stays in second position. The original version is probably the most neutral everyday order here.