Worlds lost

After shutting off my android phone and logging back onto minecraft I was greeted with the the screen in the photo below. I have experienced this in the past and did not report it (it was a couple years ago). I found a redit user with a similar issue who suggested it was caused by a corrupted level.dat file and was able to fix it by using a computer to go into the files and merging worlds somehow. I'm not sure how reliable this person's advise was but I hope it will be of some use. Over all I would hope to see some defensive programming technique to stop this kind of file corruption occurring without making a backup within the programme itself in the game. Even just better guidance for reviving worlds in game would be greatly appreciated thank you for your time.