Well.... I'm not really good at giving advice.....

I, myself, am really only good at drawing living things.....

I struggle with structures and backgrounds....

Looking at the art in your gallery, I don't see any issues with it....

Something that helps me when I draw people, is that I lightly sketch a

mock-skeleton to help keep the basic structure of the subject....

I wrap muscle and fat around it when I draw....

Also using a real-life reference helps a lot.....