It’s telling you right on screen. Battery service recommended.

Means the battery’s shot. They don’t last forever.

Google how to replace it yourself, see if you’re up for it. If not, find a service to do it. Doesn’t have to be (probably shouldn’t be) the Apple Store. You’re LOONG out of warranty.

I just got an R36S for ~$36 shipped from Alibaba. It’s awesome out of the box, but you can tweak. It’s incredible what it can do at that price.

To son proof it, just grab an image of the SD card before he starts mucking with it. Easy to flash back to a known-good starting point.

You can even back up his customized version when he has it mostly working before he mucks it up again.