Good so far! A couple of things I can suggest: Try to always make sure the lines converge towards the point that's further away. And the curve will be more pronounced the further away it gets from you. Those should give your cylinders a bit more believability. Good luck!

Cool! Yeah, warm ups can really help. I'd say, just keep going with the course and do the exercises and you'll learn a lot I think! For this particular warm-up you could try going for a wider variety, in terms of size for example. Some really small ones, contrasting with really large ones. Maybe try organizing them on the page, in a way that you find pleasing. You could also play with the line thickness. Maybe try some where the lines are uniform in thickness, or something else. In the drawings you've posted the bottom of the hat ellipses tends to be darker on the right side. Maybe practice doing the opposite. I hope this helps :)