Of can mean mean if only if that word can be replaced by whether. And indeed it also can mean or.
Indeed, als cannot be used in this sentence. Als is used when if can be replaced by when (without changing the meaning of the sentence).
In this case, Dutch is similar with Chinese, which if (whether) and if (when) are different words.
That makes it easier for you. I guess if you link the Dutch of and als to their Chinese translations in your mind, you'll always pick the right ones when translating if from English to Dutch.
Mits = as long as: 'Ik ga morgen naar de dierentuin, mits het niet regent' (I'll go to the zoo tomorrow, as long as it doesn't rain).
The opposite is tenzij (which means unless: 'Ik ga morgen naar de dierentuin tenzij het regent'), but even a lot of Dutch people mix the two words up.
They are close, but in my experience they aren't usually used in the same context. You need a linguistically educated native speaker to explain that one - I just use them in conversation/correspondence.
Neither mits nor indien means the same as of in this sentence though - that's more like 'whether'.
Raahiba as per you, that leaves the words mits and indein with very less or no distinction.
- If/when it rains, the street gets wet.
- Als het regent, wordt de straat nat.
Maybe think of it as the last word that remained when "whether or not" was shortened.
(Note that this is probably not the actual etymology. I guess the real reason is accidental convergence. The German cognates are ob = if and oder = or.)
I don't know if this helps you but it helps me to translate it into what I think of as "shakespearean english" and then into modern english. So "Ik weet het niet" becomes "I know it not" and then "I don't know it" "Hij weet niet of het rood is" becomes "He knows not if it('s) red" and then "He doesn't know if it's red" Don't know if that's confusing but it helps me wrap my head around it :)
Weten is about knowledge, kennen is mostly about acquaintance:
- Ik weet niet, of ik hem ken. - I don't know if I know him.
English cognates are to wit (old meaning preserved in witness) and (chiefly Scottish) to ken (primary meaning similar to Dutch one exists in Scottish unkenned and in British dialectal to misken).
PS: The difference is the same that also exists in the modern Romance languages. E.g. in French: "Je ne sais pas si je le connais."
PPS: An overly literal translation of the Dutch sentence, using only cognates: "I wit not if I ken him."
It is technically correct, but it is not normal, idiomatic Modern English. Modern English has obligatory do support. Instead of "he knows not" you have to say "he does not know".
Because the closest era to which it looks like is still not the case. 'Tis not the Shakespearean time, lad/lass.