Welcome to Industrial Design. As you've probably learned, it takes a lot of hard work, practice and dedication to develop the required skills but the amount of tricks and creative energy you can bring to the table is undeniable. It's a fun (challenging) ride. Glad you've started and aren't afraid to share your work (this is the problem most beginners have).
I've been in your shoes (as most of us have) but if you continue to sketch daily and gather inspiration from masters of their craft you too will be able to communicate visually. If I were you I would go buy one of these books "Sketching the Basics", "Sketching, Drawing Techniques for Product Designers" or "Design Sketching". All excellent reads/examples of how to learn the fundamentals.
I would also check out of my fellow alumni, Reid Schlegel. His website on Behance has some great tutorials https://www.behance.net/gallery/2334387 ... -Tutorials
On top of that his Instagram is loaded with top notch photo realistic renderings to give you inspiration.
As far as critiquing your work above I'd say:
1) You need to gain control of your pen more. Once you can sketch a single straight horizontal line, you can sketch anything.
2) Understand the principles of perspective. Vanishing points for 1 point, 2 point and 3 point perspective will help control those horizontal lines.
3) Know how line weight will affect the way one reads your drawings. This is crucial for making your drawings pop and understanding what is overlapping what.
These fundamentals are expressed in depth in all of the examples I listed.
Best of luck,