Items and buildings disappear on leaving the world

Whenever I leave the world and enter, all the items I put in my chests will disappear.
When I step out of my world and enter, all the blocks I put in disappear.
When I leave and enter my world, all the blocks that I have destroyed reappear.

These three things happen whenever I leave and enter my world.

Samsung galaxy j3
1.3Ghz quad core
1.5GB RAM

Notes: This happened to a world created in version 1.0
Only items that are in my inventory do not disappear.

Samsung galaxy j3