I went to play League the other day and the client just showed a black screen and kept doing so after I restarted my PC so I uninstalled and reinstalled the game which worked however it made the client extremely laggy, even on low spec mode.

I uninstalled and reinstalled again and I was given a 1.3gb update (https://i.gyazo.com/0554e5bfec50e00c7307548b5595cfea.png) which would take over 300 minutes to install even though I have a 38gb download so it really shouldn't take that long but I let it download anyway until it got near the end and give me this (https://i.gyazo.com/ca72fab32e54e06304f8ec71c562fc12.png), I'm honestly lost what to do and how to fix and I'm wondering if anyone's had this problem before and they know a solution?

Edit: Run it as admin and got this (https://i.gyazo.com/f4e175d44f34dc401dbd4412663dffde.png) but any solutions in case it doesn't work are welcome.