Difficult to remember Hvorfor=Why... It confuses because it seems like "What for" :---. I'll try harder
The thing that makes me remember it is the word "wherefore", which is a very old English word that actually means "why". I remember that because suddenly the phrase "Wherefore art thou Romeo" from Romeo and Juliet made no sense to me when I learned that. "Hvor" means where, so "hvorfor" obviously has the same root as "wherefore". That may be only marginally useful to some people, but it helped me.
Confusing it with 'what for' is actually how I remember it in the first place :) same meaning. But as someone pointed out in another question, it's more like 'wherefore' which in old English means 'why' as well. Similar stuff in German too.
Why cant I translate it into "Why do you make food?". I don's see any direct implication that it's present continuous. I am not a native English speaker so it gives me a lot of troubles not necessarily connected with danish grammar.
I am a novice too, but I think there there are no distinction in danish, same thing as in french where other words in the phrase would specify if he's doing it right now or not