Mirre, you are deffo improving. Some small pointers on perspective (I am not a perspectivehero either but with more construction it gets easier)
The perspective you have is quite distorted, the people whatsoever are not. Technically they should. And they also don't really follow the general perspective of the picture.
For shoulders, hips, eyes and such which are level to the ground you should be able to draw a perspective line through them which goes to the vanishingpoint or horizon, in this case more or less vanishing point as they are seated around the table which the perspective is constructed around.
Esp. the black girls perspective is rather wonky, we should be able to see more of the top of her head, as I think she is meant to just have here head rotated towards the blond guy and not tilted. ATM it looks like it's tilted to her right. Same goes with her right shoulder, we should see that, unless she is an amputee
and as her right are is atm it is stuck in the table.
Generally in this pic the black gal and the blond guy should be quite a bit bigger than the other 2, esp the other guy.
Because you have drawn the people as if they are at the same level of distortion and depth the guy in the back becomes an optical giant.
Compare his waistline in comparison to the edge of the table with the same ratio of the black girl's waistline to the tableedge on her side. HE IS WIDE LOAD!
Headsize issue as mentioned by Helm, and I am sure you know that yourself. Try constructing a tiny bit more.
Also your ellipses are all rather wonky. Circles in perspective are not easy but follow definate rules of perspective (tho you have to think a bit more to deduct them by yourself)
Nice things to know about ellipses in perspective
http://www.abadjiev.com/konstantin/sheldon/ellipse_lesson.jpgAnd something more basic, you seem to be suffering a bit from what he mentions at the very bottom.
http://www.abadjiev.com/~deviation/konstantin/sheldon/cube_lesson.jpgKeep on keeping on!
