Nicest job on your very first post, JianPhoenix. Nicest job on your 1 hour class drawings of the figures so far.
So my suggestion is two critiques: 1) your lines are farther too itchy for your own good. 2) your gestures need even more looseness and freedom of emotion inside. Would you please loosen and speed up your dominant and non-dominant hands with your first ever 30 minute class mode (if you haven't already)?
The reason why you could and should do this suggestion or two is as a result, your lines and lines of balance will become the most weighty, lively and cartoony and exaggerated in your quick sketches.
For more inspiration, be sure to look up the Proko videos for free online on YouTube on gesture drawing. Good luck to you and your goals.