It is from the lens itself, I noticed this a few days ago, when I leaves work under the 5:30 sunlight.
I decided to purchase a screen/finger smudge protect and it reported glare too but it doesn't do any of it.
When backing up under the morning or 5-6 o'clock sunlight, the camera is close to blind. This is the worst camera and screen combination I have ever had!!!
Technically, there is a trade off to be made between overexposure in overlit conditions and underexposure in dimmer conditions. Have you tried the narrower angle, that might help?
The dark screen is an easy fix. On the bottom left of the screen there is a moon/sun (brightness) button. After putting it in reverse press this icon it will make in "night vision" and very light and clear.
It seems that the terrible glare was caused by my choice of the widest angle, I have set it to the medium angle, now it is OK to me. I really hope there could be an auto mode for the camera to set its exposure and angle, that actually shouldn't be difficult to implement. Thanks for everyone giving me advice!