This is a really generic, basic, simple 4-door sedan. And I mean that as a complement. The shape almost looks like every ‘4-door compact’ on the market in the U.S.A. right now, so you’re doing good.
It’s maybe a little late for general shape critique, but if you’ll accept the critique, I’ve got a few things to point out;
First, the rear door doesn’t follow the fender curve all that well. Most cars with seats that close to the back axle follow that curve around the rear wheel, so it looks a little funny when one doesn’t. If I were ‘tricking’ your car out, I’d totally put a spoiler that came up from the wheel well to just above the rear window, matching that line, but for a simple sedan, it just kind-of throws me off.
Second; I can’t really tell if you’ve added the ‘gaps’ for the ( boot / trunk ) sheetmetal yet, but it seems where the corner of the B/T would be, the lens covers on the tail lights are ‘creased’. I would suggest either making the lights two separate lens covers by splitting that light along the crease, or maybe smoothing it out a little.
These are, of course, just ideas. They’re just what I wouldn’t expect to see on a real car, is all.
I’d like to see the front, or maybe even a .blend <<hint hint nudge nudge>>, but overall I’d say your topology blows my skills way out the water. Try adding some small details, though; it’s not a car until it’s got a whip antennae sticking out the top!