The "shadow" is called ringing and caused by the print head shaking after sharp turns. Try tightening your belts and check that the hot end is fastened properly. Too high jerk-settings in firmware can cause ringing too.
The holes could be from too much retraction if you have set random placement of z-layer start/stop point.
If not, it could be uneven extrusion. Perhaps your extruder Gear is not tight enough and slipping or your filament is bindning?
