Hey @De_maan… It kind of looks like you deleted files from the engine as well, or at least something they relied on. Try to uninstall and reinstall your Unreal Engine installation.
Also, I don’t know if this is what you did, but DO NOT delete files from outside of the Editor! Use the editor for that! Because it has to fix up redirectors after, there’s more to deleting here than just removal. 
Hope that works for you!