Downgrading 9.0.83 Google Play Services manually
I solved the problem for my Huawei P8 Lite Android phone like this:


I unlocked my bootloader 
I rooted my phone 
I succesfully checked with Root Checker Basic that my phone is rooted
I downloaded and installed System App Remover from the Google Play Store.
I put my device in Airplane Mode in order to prevent auto upgrade of GPS.
I opened System App Remover and select "System App" from the menu.
After I found Google Play Services in the list which was marked as "Should keep" I selected it and pressed "Uninstall". I ignored the next warning.
Using Settings/Apps, I saw that Google Play Services "Uninstall Updates", and "Disable" Buttons were no longer be grayed out.
I pressed "Uninstall Updates"


Here is the result: Downgrade of Google Play Services to 8.1.18