Lenovo — bad quality handset

I have purchase lenovo k6power 4month ago.. After using few month i have face many problems in this handset.. Some times it's display automatically work and also vibrate and power off /on button not working for that problems i cannot switch off the mobile and the touch not working.. And handset is hanging continuously.. I was call lenovo customer care they have suggested to update the handset in android 7.0nougate. I had do this but i face same issue.. And in safe mood the handset is hanging. I have done everything like safe mood, reset and hard reset but same problems it arise. So plz suggested me what could i do for this???