Salam Dominique
I understand now what is meant by quiz activity context. I created some quizzes saving the question in the quiz context category (default ...). I succeeded to duplicate quizzes and the original questions were not overridden.
So far so good.
However, I don’t see any new categories for the new duplicated quizzes. I only see the original quiz default category with the original number of questions. Namely, I see neither the categories (of the duplicated quizzes) neither the new questions of the new duplicated quizzes!!