Welcome to the community. 
First of all, processes getting stuck in the background is a known, unfixed Windows issue that has been around for a couple decades at least. I’ve experienced it myself with other non-WeMod software. The main fix is to launch Task Manager and end the stuck process from there. Or restart your PC, which is the longer way of ending the stuck process.
Installation issues are caused by interference from security programs on your PC or network. This should help: I can’t Install WeMod / "There was a error installing the application" - #2 by Ravenfyre.