Windows 10: Why isn't windows installer working even though it's running????

So I've been trying to install Libreoffice since I gotta pay for office 365, but every time I try to install Libreoffice, it always downloads as an unconfirmed file. I try to open it, but it tell me what would I like to open it with. I try to find windows installer on the list, but it's non-existent. in fact, it's so non-existent that when I try to search for it in the search box next to file name, it basically tells me that it doesn't exist even though it's running in services. However, the windows installer issue only seems to be apart of the problem. I noticed that there's other things th

:)