Hello Chromatic Lera,
I've struggled with foreshortening for a long time, until I saw the following video:
https://www.youtube.com/watch?v=2jPt2BENhRA
It really explains well how you should think about foreshortening and perspective.
Another thing that helped me is I took a model using an online model poser and started drawing it from a pose that I was comfortable with (not foreshortened).
After I roughly drew the pose (no need for a detalied drawing, you just need to get the hang of the volume of the major shapes, drawing with boxes is also fine) I started moving the camera a little to make the model seem more foreshortened (Just a little bit), now I draw the model from the new angle.
Continue moving the camera into a more foreshortened angle each time until you've reached the maximum level of foreshortening.
If you've reached the level you want, congrats - you now can draw foreshortening!
It takes time to master it, but keep at it!
Hope this helps!
