Not sure if this would help, but I think of them as "word pairs". So we've seen the "... có... không?" phrasing before. You can simply ask "Có không?" (Does it?) if the context of the question was already understood. The phrase "... muốn... không?" can be simplified to "Muốn khống?" (Want it? Want to?). Again, that only works if the context was understood. Hope that helps?
The location of không is important. If it comes before the verb (muốn), then it's a negative. Here, it's just a question.
Vietnamese people say this so often! Why do they always want you to sit down even when it is not convenient? haha