These show you have a good basic understanding. One piece of advice I thunk you could benefit from is sketch first, render second.
The things you should be exploring, defining, and communicating in the sketch are the core idea, proportion, function, aesthetic concept, rough concept of manufacturing approach.
Once you have those things sorted you can begin to render color, material, finishes in a persuasive way.
It becomes difficult to evaluate these sketches because the core idea is not evident yet. What do these product do? What scale are they? The answers to these key questions should be evident in the drawing.
For example, I might guess that the first sketch is a handheld vacuum? Is that the best view to show the design? Is the handgrip proportionate to the body? Should there be a larger disc collection chamber and motor housing?
I’d love to see the answers to these questions in some follow up sketches.