Oh my...
Before we go anywhere else... one thing to begin with:
see the difference? (it applies to ALL of Your drawing)
(note that black used for contour is NOT the same as black used for "paint")
(left - as is, right - as should be)
Next thing - the 15-7 marking on plan view: it is left in blurry multiple-shade format - in FD it's possible to use as little as 4 shades of any given color (though I use 5-6 - but 1-2 of them in minimal amount). (and in fact Your work is completely lacking any shading at all)
And here's the (oversized) example of shading: (gradation from brightest to darkest: yellow - orange - red - maroon - purple)