This is my second time using this page, and I would like you to help me with my drawings, please give tips so that a beginner can understand them, in drawing of 10- 20- 30 minutes I finished before time, I did not know how to handle my time t_t
Your drawings are very good considering you are a beginner, so don't worry too much, eventually you will know how to handle better your time, just keep practising.
You may try to clean a bit your lines. For example, the 5 minutes drawing it's a bit hard to understand. Instead of define the figure by adding more pressure with your pencil, you can use an H (4h, 2h or h) for the sketch and a soft pencil (hb, b, 2b, etc) to finnish your work. Or simply try to avoid doing a lot of lines. In this way you will be able to see better what is wrong.
I like how the last draw looks (30 min), but I can't see many photos and the 30 seconds one is wrong.
Do you do gesture drawings? Check the site's articles about it if you didn't do so, they're very helpful.