Game Crashes and deletes progress!

Recently I've been working on a MCPE build project, however several times when I'm finished playing for the day I click "save and quit' and it gets stuck and freezes my iPad for about 30 seconds before crashing Minecraft PE. I go back onto Minecraft PE and it takes several attempts to get back into my world because that button also gets stuck. When I finally get back onto my world, it has deleted all my progress even though on the thumbnail for my world it shows my build. This is super annoying especially when I build something big and it gets deleted. I hope you could fix this.

Thankyou!
Caitlin T
P.S. This is happening on MCPE 1.1.1