my computer keeps saying its out of space and to download minecraft, yet it is already downloaded

Put the summary of the bug you're having here
my game is shutting down
What I expected to happen was...:
to be able to play without it shutting down on me
What actually happened was...:
it continued to shut down
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...