Why isn't 'cùng' preferred here? Typically 'cùng' is used in the sense to "be with someone".
What's the difference between thời gian với and giờ cùng?
I don't understand your question well, but if you want to use'' giờ cùng'' , in this sentence, you should use'' thời giờ cùng'',
Ex: bạn muốn dành thời giờ cùng gia đình không?
there is no difference between ''thời gian với'' and '' thời giờ cùng'',
What's the difference between "có muốn" and just "muốn" on its own?
I think with có it is much more emphasized
there is no difference, using '' có muốn'' makes the sentence sounded better in vietnamese.