The Sandbox and chest are two entirely different things.

The chest is the place where avast stores as infected detected files.
The Sandbox is a shielded environment where you can run (possibly infected) applications.
https://blog.avast.com/2012/11/16/what-is-the-avast-autosandbox-and-how-does-it-work/

Just removing a avast folder is not removing avast.
Trying to remove avast is not causing a hard drive problem.
avast has nothing to do with other installed application except that it is scanning them.

Do you even know what ransomware is ?