I am assuming that when you try to enter the game it crashes now since you downloaded the map? If so maybe try checking your particles folder for double particles first and deleting them if there are any.
If that doesn't work out it's possible you damaged, misplaced, or lost some important files and you might have to uninstall the game and delete the main folder and then reinstall the game. Just remember if you do end up doing that be sure to back up any important files like presets etc in a folder else where in the computer so you can replace them back into the fresh new install and not lose those files.
Goodluck
