Still got a long way to go but here's some pointers.
I don't know what program you're using but you'd highly benefit from learning the pen tool. Just google for 'photoshop pen tool tutorial' (or change photoshop for whatever program you are using.
Your lines look like you're just using a brush and going as straight and quickly as you can which make them not look like straight lines.
Also looks like you tried to make the VXR logo yourself. Well done for trying but it looks a bit...nasty. I've attached a decent one I made a while back that you can use. (actually attached two, one .png with transparent background with no edging details, and one .jpg with a 'metal' look and outlines)
Try find some more pics of the car (theres bound to be plenty if you look) and see what the rest of the logos on the car are. www.brandsoftheworld.com would be a good place to go when you're looking for high res logos.
Keep at it and if you need any help just shout, i'm sure someone will help if I don't.
Here's a load of quick renders for you. Sorry the scenes not all that great, it's quite old and the only one I could find which had the spoiler already removed (yes, I could've made a new scene but laziness got the better of me).