Hi @hmattoo and thanks for the detailed description of your project!
It seems that you are missing the tyres as well as an underbody. I would add those to avoid unnecessary circulation beneath your car - is this on purpose and if yes, why? For the meshing I would like to show you one template to see what the general procedure would look like: Aerodynamic Analysis
And have a look at this workshop tutorial from my colleague @drodriguez32: CFD - Ride Height Analysis. If you have any problems meshing your car then, please reach out to us once again - either one of the PowerUsers or I will jump in to help you out!
Cheers and all the best!
Jousef