Earlier quoted context omitted.
Swedish: Vad har det med saken att göra? direct translation: what has this with the matter to do? meaning: what does this have to do with it? Where does understanding come in? I can imagine what understanding mean for mathematics, science, etc. but for language, I'm having difficulty figuring it out.
The understanding comes from knowing when to use that phrase compared with other phrases that might mean similar things. Idiomatic usage to some extent. If learning a language was just remembering direct phrases then machine translation would be trivial
so the understanding took far less time than remembering. I could read a whole grammar book 10 times, but if I don't remember any of the words, then I'll never be able to write/say something.
having all the words on the tip of my tongue is no good for communication.