The b23expertss32b_only.challenge.gbx file you have requested: Maps Levels Missions / Tracks / Fast Tech / Experts Only - 5.08kb is not available. Perhaps try browsing all files for the game TrackMania Nations Forever and upload any files you want to share or are missing. This is the only information we could locate:
place the map in your Game Data/Tracks/Challenges/Downloaded folder Please only play this track, if you are an expert. Otherwise you couldn't even stay on it for more than five seconds.