Turn your phone off. Open iTunes in your compute Press and hold home button while plug it with the computer and release the home button once you see the itune and cable sign on the screen. Same time you ll see you phone is connected to itune and will ask for restore or update. I would suggest you to restore it. But you can try updating it first in order to save your data. Don't unplug it until the process finished
The answer is cold press farm. It's the Bazel of the screen which is cheap quality. Solution: see the picture and pres with the screw driver or some metal thing to lessen the gap between the hings so they will hold the the LCD properly. You have to press harder to fit the LCD in but once its dose. Will fit properly.
I fixed so many backlights specially on 6 and 6s. Normally it's filter But recently I d given iPhone 6s with very low backlight Checked all caps, filter, diod, coil etc. Everything seemed fine so I changed backlight ic(u2040) no luck And than I changed main pm ic and problem has gone.
The best way to give a good quality is using OCA instead of LOCA- but that method is gonna b expensive- coz you need autoclave vacum machin to get rid of bubbles. So the second best way is as younis said take the back light off- but you need to make sure you are working in dust free workplace. Or try sugru on the sides of lcd to prevent LOCA between LCD and BACKLIGHT- If you are very good in alignment of GLASS and LCD- coz you can not use mouldy if you use sugru