I would concentrate on getting the perspective correct by sketching the basic building blocks of your sketches first. Having said that, the Space Station is pretty good perspective-wise, although the two vertical chimneys are a little off, and I think the marker work isn’t doing the overall image any favours.
I’d loosen up a little, leaving construction lines in a sketch isn’t a crime, and adds to a sketch’s “designer” feel. Be confident, draw straight lines from your elbow, curves from your wrist, and spin the paper so the line you’re trying to draw feels most comfortable.
An understanding of perspective is important, but not the be all and end all of a sketch’s success. TBH, both near-side wheels of the Dump Truck aren’t sitting exactly as they should, but the overall look and feel of the sketch is unaffected.