Welcome to the forums @UmaShanker!
I have not downloaded the 3D model to look at it in Blender, but my guess is that it is using a Mirror
modifier, and when exporting the modifier is not applied and therefor only half of the car is shown. I would check the car body mesh and make sure to apply the Mirror
modifier or check the apply modifiers
checkbox in Blender when exporting the GLTF file.