I'd like to point out 2 things here

1. all of your constrctions are lacking line weight and shadows filled in with solid black, which makes it really hard to understand how these parts exist in space. Your elephant is an example of this effect, as I can't make out the forms with all the noise. If you dont have a brush pen or thicker pen to fill your cast shadows with, still fill them as solidly as you can with the pen your using. A half-hearted effort will just create a focal point and draw your veiwers attention to it. Uncomfortable mentions that in his cast shadows video. If your worried about your pen, I tried it in lesson 2 as i didnt have a brush pen either and it did get use up faster, but the clarity and understanding it gives is well worth it.

2. this is something you can take with a grain of salt as I am currently working through this lesson myself. You constantly added forms to your bluebird construction, which isn't a very good idea as it adds noise and breaks up the bird as a whole, ruining the solidity. Try to stick closer to uncomfortable's method and imagine that your merging your forms together. Sorry if that comes of as a dumb platitude but it's the best I have.

good job forging through though

edit: I looked at your sketchbook and I think you should focus on your warmups and understanding each task and the units of work they consist of