By the way - you need to learn to make components of sub-elements of your drawing as you go, to keep your geometry from all sticking together and making it impossibly difficult to edit. Your drawing of the side is beautiful, but should be made of at least several, maybe many, separate components - doors, windows, side panels, speaker, marker lights, air con on the roof, roof itself, etc.
And do you have overall dimensions for the vehicle? I can see dimension arrows on the PNG image, but no measurements. Your draft vehicle is approximately 1321mm long and 208mm wide, which seems improbable either for full size, or for a scale model - FAR too small for the former, and too large for the latter.
What scale will your 3D printed model be?
Try drawing it to the exact size you want - either full size for the ‘real thing’ if you have dimensions for that, or scale size, if you know what you want to end up with. I’d recommend full size, then scale the whole thing down when you have finished, using the tape measure tool.
I’d suggest you make separate components of the plan, side and front elevations on rectangles of the correct size, to get your overall shape and sizes correct, by importing and positioning the 6285.png image as a texture.
And you have used arcs for the side profile of the cab front. They are straight lines in the image, which will make the surface MUCH less complex.
Sorry, that’s as much as I have time for tonight - midnight here in the UK.