I was using the windows 10 game mode to play Minecraft and it was normal at a first moment but it started to run so slow that my entire computer almost crashed when the Xbox stats loaded, I managed to load my world and my computer's screen crashed and shut down; I forced shut down to recover my computer and I was able to do a backup before all of this so nothing happened to my world; the original files were corrupted and the world did not appear in the game so I searched its level.dat and was filled with null.
I switched down the game mode since all of this happened.
Thank you for your report!
We're actually already tracking this issue at MCPE-35692, so we will resolve and link this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated. (Thanks for including the world save though, it will be useful to see what has happened.)
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