Hey Chiara,
Congrats! These turned out amazing 👍
In the grid proportions piece: don't worry about having used symmetry, but I do recommend trying a few times without it so you can train your eye on how to achieve that yourself. The woman figure is really, really good! The man figure feels a bit blocky (with a lot of hard edges) and the forearm appears to have a weird shape that follows the pelvis. But other than that, you nailed it 😬👍
About the basic structures: it's actually a nice thing that you were able to go to the circles instead of the blocks in this case, it just adds to your "set of tools" being able to use whatever you need depending on the situation, and the result here is awesome! Congrats.
Keep the updates coming!