The last thing here is to put down a nice, solid cast shadow. I'll always draw these as an outline first, before deciding whether or not I want to fill it in. In this case, I decided to go ahead and fill it with a solid black to make the rest of the car pop (when working in ink, you may want to use a brush pen for this - just be careful not to let it go outside your set outline).
I've also put down a little bit of detail - nothing rushed, but nothing particularly distracting - to the ground to help make the drawing feel more natural. Lastly, I leveraged a puddle near the front wheel as an opportunity to put a few more solid blacks to balance out my overall composition.
As I said when we started, if your construction went catastrophically wrong, that's not surprising. This is a complicated task, with many layers of construction and a significant amount of dependence on the skills you've developed through these lessons. It's no longer all about putting each and every simple form down on the page - due to its complexity you're forced to rely more and more on your mental model of 3D space, your ability to visualize or at least understand how those forms interact with one another, and your ability to pivot in response to problems and mistakes that may come up.
I'd recommend that before you attempt a car like this, start with something more like an old vehicle from the 1920s, like the Ford Model T, or even a boxy Volvo from the 70s or 80s. It's not a simple one by any stretch, but it is going to lend itself a little better to bridging the gap between what we've tackled so far and more modern cars.