well i do hope you get it all sorted out. i'm waiting for your next one. nice to have you back here by the way 👍
I think it's over saturated. And the watermark, it'll look better if you use the clone stamp tool instead of just making a box with a similar color.
But keep at it. I know Pink the Floyd has some GIMP tutorials that can help you out.
Welcome back, mate!
Like Driftnewb said, it's oversaturated and the car's a bit dark (yeah, I know it's black).
Also, about the watermark, it would actually be better if you cropped about halfway through the dirt part of the image. Not only it'd compose the image better, it would get rid of those bad textures on the sand. 👍