Let me say that you shouldn't be negative. Lets focus on the positives: Looking at both the rear and front views of your sketch, you've got a good sense of perpective. Some things you can work on: Try widening the rear a little bit and make the car a little flatter, just a little cos right now its a bit bulky. From the front, looking at the windscreen, resketch the car adjusting the A-pillar on the far end by tilting it back a bit. Your car is curvaceous, so that little adjustment might enhance the sketch a little more. And another comment on the finish, i presume you used colour pencils. There's nothing wrong with that, but if you want clean lines i suggest you use really light drawing pencils like 2H to 5H, then to finish off you could use a well sharpened black or blue coloured pencil or fine pointed marker pens for your edges. Those are just a few things you can try...keep at it, you're doing good.
