how to fix the creases after solidify and why it occurs? Currently doing blender sport car creation course in blender 2.8. Followed step by step but also those pixelling after solidify doesn't go.
This is z-fighting. It happens because of binary rounding errors when you have very thin/ overlapping geometry compared to your viewport or camera clipping range. Do not solidify your geometry before using a Shrinkwrap modifier, if you need an edge, use it after Shrinkwrap. Also you do not need all the geometry that is not visible, so you can have rim only: 



You have sides of the surface in vertex groups so I just selected the inner group and deleted it to fix the issue in the screenshot. You could have the Shrinkwrap modifier before solidify there if you needed it.