I too am now completing Lesson 3, so take my advice for what it's worth.

I'm impressed with your work! Really excellent, overall.

The one thing that catches my eye is the degree of your ellipses as they travel through perspective. On your branches, I see that sometimes the ellipses don't inform how the branch is moving through space - as they sometimes appear all the same degree. Here is a link showing an example of what I mean: https://imgur.com/a/lpxeUSP

See how the ellipses change their degree as they move through perspective.

The only other suggestion is to keep working on textures. Using a range of textures, sparingly, is quite useful to informing not only the surface of the object, but its light and shadow.

That's just my 2 cents. Overall, you are doing very well and I applaud your work.