Welcome to the community. 
Processes getting stuck in the background is a Windows OS bug that can happen with any software. There are two fixes:
- Launch Task Manager. Locate the software’s background process which is stuck. Right click it and end Task.
… Or … - Restart the PC.
As for the failing installation, that’s due to a security program on your machine or network interfering. See here for the steps to resolve it: I can’t Install WeMod / "There was a error installing the application" - #2 by Ravenfyre.