Why isn't, 'You have a book?' a sentences similar ever accepted? Or is that not proper in any language?
I am guessing it's because formally, you need the "do" in English to form a grammatical question. In Hebrew there is no additional verb and so this is grammatical (although some people would insist you need האם). So translating something that is formally grammatical into something that is not, is not accepted.
You are right, but along the same lines Almog presented, they can't possibly account for every variation. Tread lightly.
"Have you a book?" is a normal English variant of this translation, comparable to "Do you have a book?"
Ihave no idea how to do nikkud. There should be some kind of instruction with the course if that is expected!
It's not needed but is good to know for pronunciation. I use keyboard app called Swype, there's many others. To learn pronunciation make sure you look at modern Hebrew not biblical. I like YouTube channel linguistix. Fluent forever/Gabriel Wyner & jbs Jewish broadcast /shofar TV both have great videos too. Linguistix: Hebrew Pronunciation for English Speakers: https://www.youtube.com/playlist?list=PLfwqVVFqlT1v0tS9hhTg7kL1cUVyO4oFY
Yarden has the difference below. One has nikud (diacritics the other doesn't. That means just from the writing, you can only tell specifically which is masculine - for pronunciation). it should have been for feminine, kaf sofit, imho, ךְ You can see more under the Pronominal suffixes section: https://en.m.wikipedia.org/wiki/Suffixes_in_Hebrew ) and at https://www.cartoonhebrew.com/chaf-sofit
(note I am learning not a native speaker). This is all in the tips and notes for the course. you can see them at the duolingo website (put your browser in desktop view to see all offerings), or my favourite ways:
organized by skill in one pdf for the whole course: https://www.docdroid.net/JnfmyEV/tipsnotesbackup.pdf
Replace your username where mine is for information on your progress and the tips and notes, etc: https://duome.eu/teribleteri/progress
We learned in a school that "have you a book?" is (may be older) british form. "Do you have a book?" is an american style. But i am not a native speaker, so i would prefer to keep lingo grammatically correct. I do not want to destroy my weak knowledge of english grammar. :-)
British English: Have you got a book? / American English: Do you have a book? ;)