This article explains the best practices for anyone with an Android device that will help you achieve optimal backup efficiency.
The backup process on Android is most efficient during the daytime. We recommend you connect your phone to a charger during the initial backup to speed up the process. During the night, you can expect your backup to run slower due to operating system specifics.
If you want to speed up your backup, you can go to your device settings (the gear wheel), then Proton Drive, and select Unrestricted battery usage. Please be aware that this might drain your battery faster than normal. We recommend you return to Optimized mode after your initial backup is completed.