Hello. I'm just going to move your question into the Quiz forum where you will get more specialised help. I don't know if this is useful but there is a page in the documentation Quiz Subscores which might be interesting.
Quiz
Dividing questions into grade categories
دا بحث کولپ شوی دی نو تاسو نشئ کولی دې ته نور ځواب ورکړئ.