I'm sorry if any of this sounds harsh. It is not my intention. I like the concept. It's a lot like TrackMania, but it has a lot of issues I'd like fixed before adding new features.
My main issue is the physics. Mainly the lack of gravity on the car. The 1st turn on track 1 makes you just fly off unpredictably. This ends up as just having to reset over and over on the 1st turn of the game. That combined with the lack of slowdown when hitting walls just makes the car launch into space if you hit the wall even slightly. Those physics just don't work well with the TrackMania style levels with sharp precise turns. That doesn't have to be a bad thing however.
Track 5 showcases sections where the physics are very well utilized. The long tunnel sections with obstacles are incredibly fun and it's where the game really shines. Focusing on that would be a really good idea. It also gives it a niche that's split from just being a "TM clone".
I love that you added a map editor instantly. The car color customization is also great. I also like the look of the game just wish the lighting was a bit better on some parts cause the road can get really shinny at parts.
All in all I've enjoyed the game and I see a lot of potential for it in the future. It'll just require a good amount of work to get there.