My nexus 7 2013 32gb storage decreased to 11gb? How to fix it?

[Shikhi]

I maybe didn't clear the data of my nexus 7 before installing android 5.0 from computer. But I think its not the reason. I had a root on android 4.4.4 and it must be something with that.

 

[Aliandren]

Use your custom recovery to format (not wipe) your partitions, then reinstall the official factory image. Probably want a backup first and drop it off onto your computer.