Body should be longer horizontally, and its legs taller. Maybe his shoulder is a bit too towards the extern, should be placed a bit more into the body (let's say more on the left, as if going to the center of the body.)

If you don't feel sure about anatomy and proportions, simply go on with the drawing and don't look at it until the next day. It helps your brain to detach from the picture and rest.
Also flip it horizontally, vertically and in every possible direction, even rotating it, to help you see more hidden errors or imprecisions!

Thanks again,
I made some improvements based on your help and a new reference.

Alrighty! Will wait for it.

To draw down feathers and feathers is really hard, I want to draw the most realistic I can, but I think I put too high demands on myself.
Everythink I did until now is by far not as I wanted it, BUT I will never give up and with every stroke I am learning more :)
For now I need a break.

You deserve it.
As for feathers, you can choose: draw every single one (+detail), draw some more detailed ones where they are plainly visible over other less detailed ones (a good compromise) or draw a bunch of small-detailed ones (+quantity and general detail, the best one to start practicing).

And keep it up without surrendering!