If you already own NFS: Shift legitimately (e.g., on disc or via GOG/Steam if still available), I’m happy to help you troubleshoot, mod it safely, or write a detailed guide on from the official version.
The base game is known for "floaty" handling and technical bugs. These mods are highly recommended by the community: NFS Shift is finally good?! Overhaul Mod 2.0 in Description need for speed shift fitgirl repack better