Great dialogue usually comes from two things: inside knowledge of your characters and tons of revisions and rewriting.
Each character has to be unique and must have their own voice. Be sure that all of your characters sound different from eachother and ensure that there is a consistency in their voice. For example, Dumb characters don’t suddenly become intelligent unless something happens, like they go to university or acquire magical powers etc. If all of the sudden your dumb character starts quoting Shakespeare for no reason, your reader will be confused. With speaker tags like “he exclaimed,” “she pronounced,” and “he spoke angrily” are totally unnecessary and possibly even distracting.
Death: Think about all of the novels you’ve read. In how many did a character die? Most of the greatest stories often involve death. , The Hunger Games, Harry Potter Charlotte’s Web, Where the Red Fern Grows, and so many more all had main characters who died. Death is universal because one day everyone will die…I guess you could always write about taxes instead.