I have a Vodafone Smart Turbo 7, and somehow have selected a setting that causes the Display settings to revert to a low brightness level and a 15 second Sleep delay whenever I switch the phone off. As I live in an area without coverage, and only get to town once or twice a week, the phone is switched off most of the time.

When I switch it on, I set the brightness to a suitable sunny day visual setting, and the Sleep timing to 2 minutes. However, after being switched off and on again, the settings are back to a low brightness level and to 15 second sleep mode.

To try to keep the battery usage levels low, while asleep, I am using GREENIFY to swith off (hibernate and sleep) all apps while in a coverage area.

How can I retain the settings I have selected?