Learn Hardcore Afrikaans: Alvorens ons die tandartspraktyk besoek, lees ons die verwysingsbrief. - Before we visit the dental practice, we read the referral letter.

It is correct Afrikaans, but it sounds more formal or written than the word many speakers would use in everyday conversation. In ordinary speech, people often prefer voordat.

So this sentence could also be said as:

Voordat ons die tandartspraktyk besoek, lees ons die verwysingsbrief.

Both are correct, but alvorens has a more formal tone.

Why is the word order ons die tandartspraktyk besoek and not ons besoek die tandartspraktyk?

That is because alvorens introduces a subordinate clause.

In Afrikaans, when a subordinate clause is introduced by a word like alvorens, voordat, omdat, or dat, the finite verb usually goes to the end of the clause.

So:

Main clause word order: Ons besoek die tandartspraktyk.
Subordinate clause word order: alvorens ons die tandartspraktyk besoek

This is very similar to Dutch and German-style word order, and it is something English speakers often need to get used to in Afrikaans.

Why does the second part say lees ons instead of ons lees?