Nice work @Chiara Benedetto! Hands are difficult for everyone! I think the biggest issue with these is that the entire metacarpal area (the palm area) seems too small compared the finger lengths. The palm length (metacarpals) is about the same as the fingers (middle finger actually), and it looks like many of yours have that area smaller than the finger length. It is difficult to tell based on the angles of some of these, but something seems off about the proportions. Just something to watch out for. I hope this helps!

Really nice drawings! Very neat sketches and clear structure. My critique here would be that i see in your drawings that the thumb shouldnt go on a 90 degree angle againts the palm since its unatural for the thumb to be able to go that far, also i see that the thumb in your drawings are a bit too long. I like how you draw a very diverse poses of the hands! Good job!!

This looks like a great start to hands, I personally have been putting it off, but something that I notice is the proportion of the palm to the fingers, you might want to make the palm bigger or the fingers smaller. I'm not sure if this is intentional, but otherwise, you are going on a great path! Maybe in the future try to put more gesture into the fingers so it looks more natural when you are done with the simplified shapes.