What will improve this ?

[Bikeracer2020]

how many outlines are you using ?

Not really sure what you mean by outlines.

It's just a rectangle wiith a smiley type face on it drawn in Fusion 360 and then just extruded up 3mm where it is solid, this leaves the face parts open with no extrusion in them and daylight shows through them.

It's for placing vertically on a fence to stop cats walking on it up to the bird table.

It's just sliced laying flat with ' Lines ' set as the infill skin patern top and bottom.