Very nice variety in the poises you are showing us. You have studied anatomy. You need a good working knowledge of the muscle and bone structure of the body. Keep work on that area up. Practice on hands & feet would be a good idea.
Keep up the good work. Remember: practice makes better, so practice, practice, and then practice some more.
You've got some great shapes and solid anotomical features. Really excelent grasp on how the anatomy should look. I especially like your feet and upper torso construction.
My big suggestion is try drawing through the forms, as if the figure is transparent. Draw out the full rings of the pelvis, the torso, and where the limbs meet the joints, so you make sure you think about the depth of the forms and how things overlap. It should help your perspective and positioning.
Focus less on the accuracy of the shapes and more on how they fit in relation to each other. The accuracy and the details can be drawn in later.
Thank you both for your advices.
I am a retired teacher (Ancient Greek and Latin) from Belgium, but living in Berlin, Germany. I began to draw about 20 years ago, but made quick a very long pause because I got a job at school and had no time and free mind for drawing anymore. Retired for the past year now and stuck at home because of Covid 19, I began nude drawing three months ago. I am gratefull for any comments, because I haven't a lot of faith in my hability to draw, but your critique shows me that I am on the right way. Thanks a lot!