Troubble by signing in my Gmail to iPhone

Hello,

Hi google . I’m Jacob. I try to find a help ,by google about a very rare issue in my email account. I tried to send a email to google,several times,and nobody has responded.
The problem is I short .that I have an iPhone, and it’s not the first one that makes very weird.
Some page in the Phone(the page that shows about location of the recent calls- that uses “location system “is flickering,and when it does,than the battery of the device is dropping down extremely fast

I have contacted Apple several times and I have physically visited them in the apple store I Europe ,and they’ve absolutely confirmed That the phone/s self is perfect,after checking the device/s software and hardware of course.but it seems to be,that something with the stuff that I put on my phone is wrong. And they are right,because I had the same problems with 4 different iPhones, and nobody can explain it.So after rebooting my phones and checking all kind of checking,it seems that the problems are appearing ,right a way when I signed in my email account to my iPhone.

and it is not an app or something like that that causes the issue! because I have tried the phone ,after rebooting ,with out any app installed!That means,that the phone self was checked,and the SIM card also ,everything looks fine ,except when I signed my email. So I ask if someone,can please guide me here ,and see what is possible to do ,the issue is extremely disturbing me !
Thanks a lot google