Germanic wordplay, I guess. German does that too: stehen <--> verstehen
Don't know about swedish, but in german "ver" is signalling a motion away, meaning you are (figuratively) standing further away from a thing and see it in its entirety.
English likes to do their own thing so you stand under something instead, but the idea seems the same.
How do you know when to add the "do" in english? I read it literally as "Understand you the book?". Is it just with practice that you know to add a "do" and switch the order of "you" and "understand" or do you just realize that it doesn't make sense translated literally or what?
In colloquial speech, English speakers often drop the "do" in questions that do not have another question word like who, what, when, where, why, or how.
"Who does that remind you of?" "What do you like?" "When do they go to school?" "Where does the train stop?" "How do you fix a car?" "Why did the dog growl at me?"
The "do" forms attached to these question words cannot be omitted, not in colloquial speech, and definitely not in writing.
However --- "You remember that?" or "You understand?" are acceptable in conversation. In fact, some people only use the "do" for these kinds of questions to show their displeasure, seriousness, or sometimes impatience. "DO you understand?" or "DO I make myself clear?" are good examples of how the proper forms of "do" are added back to colloquial speech to suit the context. Also, a teacher might say, "You forgot your homework?" after the first offense, but an annoyed teacher might say, "DID you forget your homework again?" after the second or third offense.
There is no instance where you may drop the "do" in writing, only in speech.
It's complicated for me to switch the u from "du" to the u from "boken"
Du has like a French u
Whilst boken has a normal o like the English oo in book.
Switching from one word to another is a tongue twister for me.
Hence when I want to say the whole sentence, then I can't say it correctly, it's complicated.