Help How do I get my default ringtones back?

[b0bl335wa993r]

Hello guys,

I forgot to get my phone back from my nephew and he messed up my settings, disabled some apps and tinkered with a few settings. The results are annoying and I would never let him do that again. He cleared the data from most of them to manage some space for a new game he's trying to install.

1. I lost my default ringtones. If I tap the Phone ringtone in the Settings>Sound I get no other choices but none.
2. Gmail doesn't sync whatever the sync settings are.
3. The battery saver is greyed out.
4. No volume at all!

I want to try a factory reset. But I have two games like Frontline commander 2 and I don't want to delete them. Do I have any alternative to save the obb files and the apk to install it offline (without having to download all the data again from playstore? I shall try whatever methods that are available and see if I can save at least a game. Just pour in all your ideas. I came to know that I can install the game from apk which I can get from ES file explorer, but some large games don't get installed in that way. They need those large obb files.

Update:Volume and ringtones are back after a single safe boot and a normal boot.

Update 2: The Assist app is disabled and enabling it resolves the battery saver option being greyed out.