Just watched K-pop demon hunters!!

Ok wow do i have a lot to speak of. Ok but i feel the whole demon-hunter system and some questions are never fully explained bc how did talking with Jinu bring back Rumi’s voice? How did Rumi bring back Jinu’s soul? Has Gi-wa or whatever his name was brainwashed hunters into becoming demons in the past? Can hunters be brainwashed into demons? They never tell you and did the other Saja boys die with Abby (not Jinu)? Or are they still roaming around in the underworld? ALSO who chooses the hunters? Is it a guardian? Or is it by blood? If so, did Mira, Zoey, and Rumi know each other since the beginning? What happened to Rumi’s mom? Who was Rumi’s dad?