I recently purchased an Oppo A77 (in Australia), and am very impressed by the cost of the phone and the excellent hardware (Octa-core processor, 4 Gigs of RAM, and 64 Gigs of Storage - all for AU$350, or AU$300 on special!!!).
It has taken me some time to get used to ColorOS, which is Oppo's UI for Android. Make no mistakes an Android purist will struggle with this OS because it has clearly been designed to mimic the iPhone!
Once I got my head around the fact that there is no traditional Android menu and that all App icons must live on the home screen (just like on iPhone) I began to enjoy using ColorOS.
However there are at least two functional issues which I have noted with my A77, and the most glaring of these is the fact that it does not do Push notifications by default for almost all apps.
To make things interesting there are four individual settings, in four different locations, which must all be set correctly for Push notifications to work!
Section 1 - Add Apps to Startup
In order to save battery the A77 only starts what it sees as essential Apps.
As a result the first step in our process is to enable Apps at startup for which we wish to receive Push notifications.
a). Open the Security App (looks like a 'shield with a tick inside' on my A77)
b). Click on Privacy Permissions
c). Click on Startup Manager
d). Enable Apps which you want to startup with the phone (e.g.: Yandex Mail)
Section 2 - Enable Apps for Priority Notification
a). Open the Settings App (looks just like the one on an iPhone!)
b). Select App Management
c). Select All
d). Select an App of interest (e.g.: Yandex Mail)
e). Select Notification Manager
f). Enable Priority Notification
Note: You may also (optionally) want to enable 'Notification Light Flashing' to make it easier to see when a new message is present (should you not hear the phone)
Section 3 - Stop Apps Optimization
a). Open the Settings App
b). Select Battery
c). Select Energy Saver
d). Select the App of interest (e.g.: Yandex Mail)
e). Turn off Freeze when in Background
Section 4 - Lock Apps in Background
a). Start an App of interest (e.g.: Yandex Mail)
b). Press the Home button (to clear the screen)
c). Press the Recent Apps button (square button to the left of the Home button)
d). Lock App (of interest) by dragging down on it
The lock icon can be a little hard to see due to its size and transparency. Furthermore only one icon exists and it looks like an unlocked padlock. Make no mistake the unlocked padlock icon actually indicates that the App is now locked. Whereas the absence of a padlock icon indicates that the App is not locked!
At times the Security App may ask you to 'Optimize' your phone! Ignore alerts of this type as the phone is essentially asking you if you want to stop certain Apps from running at Startup; these will be the Apps that you have deliberately decided to start!!!
Following the instructions above will result in the Apps of your choice running at all times, and this does consume additional RAM, however with 4 Gigs of RAM to begin with I have not found this to be a concern. Furthermore additional battery consumption will occur, however in my experience the extra consumption is negligible.
Additional Apps which I have enabled at Startup are Carsales, Dropbox, Find My Device, Outlook, Roomster, Yandex.Mail and Yandex.Disk. Under normal operating conditions I usually have in excess of 1.5 to 2 Gigs of RAM spare despite having these Apps running.