Nah in most cultures means "No". In my culture, it means an assuring "Here, take it from me". Only family and close friends use it with each other. With a change of tone, it could also mean a dismissive "That that, sucker!" to a rude person.
"Someday everything will make perfect sense. So for now, laugh at the confusion, smile through the tears, and keep reminding yourself that everything happens for a reason." Even if someday it doesn't make perfect sense, it happened for a reason.