League is de-installed but cant reinstall it because apparently it's already installed???

Hello reddit. I really need your help.

I just deleted league from my PC because it was just bugged as hell. it kept freezing over and over again. I already asked in another thread for help and nothing helped so I thought im just gonna delete it complete. but now league buged at a whole new level.

So. I deleted league from my PC and downloaded the Installer from the page. but when I wanted to install league it said "another version of this software is already installed and we can't continue the installation." Here is a screenshot (It's german since my PC runs in german...) http://gyazo.com/117eb04ae704d5b4a82e754476319e97 It says I should de-install it in the Control option. But I already did that. but for somereason it still shows up http://gyazo.com/ac60da0bafe149186428e0d3d4956b27 and guess what. if I try to de-installt it there. it still doesnt work http://gyazo.com/7ce8fdc6fa2473ec517f5359a0d6505c When I try to de-install it, it says more or less "You can only use this option for products that are already installed". ... I have absolut no Idea what to do... League isn't at all on my PC anymore but I cant install it again. Please. anyone have an idea what to do?

TLDR; Deleted league from my PC. Can't install it again because it apparently is already installed although there aren't any files on the pc anymore...

EDIT

okay everything is even more fucked up now... I downloaded CCleaner and deleted league through it. so it doesnt even show up anywhere at all (befor it still showed up in the "Systemsteuerung" -> "Programme und Feautres" (sry idk how its called in english... this window where you usually uninstall things.)) but it STILL says the software is already installed... this doesnt make sense at all...

EDIT2

So, I just downloaded League NA, installed it and just changed in the launcher from NA to EUW... It seems to work... But I still can't install League EUW.... this just doesnt make sense O_o