World crashing

Hello,

I have minecraft pocket edition. The current version.
I have a world that is about 250 mb. Anytime I try to play it, it lets me play for about 30 seconds and then it shuts the game off and goes to my home screen of my phone. I open other worlds that are smaller and it doesn't crash at all. When I upload it to my realms server it works fine. When I make a copy I try to play it, it won't even let me open it. It ust crashes right away, and takes me to my home screen.

Please help!

Thank you

Carissa