go to update-update.rpf-common-data and backup your gameconfig (enable editmode and just drag it somewhere on your desktop) and put the downloaded gameconfig inside the folder- if u want to put in the old gameconfig in just drag and drop the old u made a backup from to openiv..
@Caseman I simply backup the whole GTA V installation folder. This way you don't need to do all the modifications again in case of a reinstallation.
BTW reinstalling the whole game just because of an error? I suggest you read the pinned comments in the troubleshooting section.
I had to reinstall it only once and that was because Windows 10 sh*tted on me and I had to reinstall the whole OS and everything else along with it.