i made this car whit subdivide but that isn't good and now i got some artifects as you can see does any one knows how to fix it i also asked it on blender forum but i think it is not a blender problem

Post wire frames.

The problems going right down the center look like bad symetry issues, like it welded too many verts together.

I agree. It must have something to do with merging vertices. Check your threshold settings.

ah thanks i will try that. bt wat do you think of the rest of the car
do you got some tips to get it better