to work as intented, please follow the instructions below.
Most Nokia phones (Power saver AKA com.evenwell.powersaving.g3)
1. Go to Phone settings > Apps > See all apps.
2. Tap on the right top corner menu > Show system.
app in the list, select it and Force close. It will remain stopped for a while, but will restart itself eventually.
From now on, background apps should work normally and use the standard Android battery optimizations.