For camera quality correction reset the camera to default settings and remove other camera apps. This should work.
For battery drain try to disable app notifications if u have a lot of apps installed and remove sync settings for optional mails.
Battery is real good for 6 plus I have tons of apps and my 12 mail accounts synced with iPhone. Try the solutions might help u.cheers
This phone very beatifull look
This phone use any ios app
thank you so much read this review