The proportions look quite accurate, although it's admittingly hard to tell because of how faint the pencil work is. Line weight will definitely help with readability of the form. :)
You are a retired teacher. So am I. It is really too bad you had to stop your art. I looked at your other drawings. They are very good. I would recommend that you keep drawing.
I tell almost everyone: Practice makes better. Keep going!
You are doing good with the additional practice. Use a darker pencil like a 4B. Also adding to bring in the muscle structure which will add impact to your drawings. I use a Blackwing. I don't know if they are available in Germany. If you look through the photos in Line-of-Action's selections, there many that because of lighting show the muscle structure to advantage (although some are too dark to tell what there).
The important thing is that you keep going.
Thank you for your encouraging words. Don't be afraid, I wouldn't give up. I practice every day more than a hour, because I like it very much and I see, I can improve my drawings this way. The first 2 minutes drawings were very light, because I didn't dare draw the line. I usually use a 2B pencil, sometines a charcoal pencil. I wil try with the 4B. I began 10 minutes drawing with some more complexe shape and I will now try to draw the muscles. (Sorry, my english isn't that good).
Thanks a lot!
Your English is just fine. I had 2 years of German in high school & 1 year in college. But that was long, long ago. I will recognize a few words now and then. Don't be afraid to be bold. If what you try does not work out. OK, no real problem. See what went wrong, correct it, and go on. For the past 6+ years, I have attended a local life drawing session. The drawing I made was done with pen & ink (could not erase). Sometimes things did not turn out well. When that happened I just went on to the next drawing (I am the timekeeper). See if you have life drawing sessions where you live. If so join up & attend regularly. You will find that your drawing ability will improve. Go for it!