Go to settings- Google - autofill - enable whatever you got saved in certain account .
Which password manager?
Is your display brightness set to automatic? If so, you need to disable that option.
I enjoy using my note 8t but just a few issues I noted. Firstly when out in bright sunlight for some reason the brightness shoots up and the screen becomes washed out. Secondly on Xiaomi you cannot copy and paste passwords from your password manager when logging in? Extremely frustrating. Other than that it's good no WiFi issues for me, phone easily lasts two days.
Bought for my son 10 months ago. No issues whatsoever.