I played on a world then when i saved nd quit it took forever to save when i got on today the world has the default picture on it and the world wont start up (the world size was 930MB and when the world messed up it went to 320MB)

This issue has been noted as MCPE-37784. I am suffering from this as well. Tell me if it accurately describes your issue.

Thank you for your report!
However, this issue has been closed as a Duplicate of MCPE-37784.

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