Learn Hardcore Afrikaans: Wanneer die internet stadig is, lees ek in die biblioteek eerder as om aanlyn te werk. - When the internet is slow, I read in the library rather than work online.

In Afrikaans wanneer introduces a time clause (“when,” “whenever”), whereas as is used for conditional or hypothetical situations (“if”).
• Wanneer die internet stadig is → “When/whenever the internet is slow”
• As die internet stadig was → “If the internet were slow”

In the clause wanneer die internet stadig is, why does is come at the end?

That clause is a subordinate (dependent) clause. In Afrikaans subordinate clauses the finite verb goes to the end (S-O-V order):

Conjunction (wanneer)
Subject (die internet)
Adverb or object (stadig)
Verb (is)

Do you have to put a comma after a subordinate clause like wanneer die internet stadig is?

A comma is recommended whenever a subordinate clause precedes the main clause, to mark the boundary. It isn’t strictly obligatory in every informal context, but in standard writing you should use it:
“Wanneer die internet stadig is, lees ek …”

Why does the main clause start with lees ek instead of ek lees?

After a fronted element (in this case the subordinate clause), the main clause follows the V2 rule:
1st position: the clause/complement before the comma
2nd position: the finite verb (lees)
3rd position: the subject (ek)
…rest of the sentence.
So: “Wanneer … stadig is, lees ek …” not “Wanneer … stadig is, ek lees …”

What’s the function of eerder as in “lees ek in die biblioteek eerder as om aanlyn te werk”?

Eerder as means “rather than.” You use it to compare two options:
• lê ek eerder voor die kaggel (“I’d rather lie by the fire”)
• lees ek eerder in die biblioteek as om aanlyn te werk

Why is it om aanlyn te werk and not just aanlyn werk?

Afrikaans forms an infinitive clause with om ... te around the verb. When you compare with eerder as, you need the full infinitive:
• werk aanlyn (verb + adverb, in isolation)
• om aanlyn te werk (infinitive clause: om + verb + te)

Why do we say in die biblioteek? In English we say “at the library.”

Prepositions often don’t line up exactly. In Afrikaans you normally use in for buildings and enclosed spaces:
• in die kamer, in die skool, in die biblioteek
English uses “in” or “at” depending on nuance, but Afrikaans stays with in for most indoor locations.

Why is there a die before internet? Could you drop it?

Afrikaans generally uses the definite article die before the concept of “the internet.” Omitting the article (“Wanneer internet stadig is…” ) would sound unnatural. So you say die internet whenever referring to it as a specific thing.