Hey c_moon, I think it's good to do these master studies, but it's kind of advanced to be trying to paint a master study when you haven't become proficient with drawing. No matter how well you match colors or create cool brush work, if the drawing is wrong then it will never look right. PAINTING IS DRAWING. If you plan to be a realist painter, you must know how to draw well. Until you know how to render a drawing correctly with graphite or charcoal, you will never know how to get your values correct in paint. Sorry, but that is reality. I did a sketch to show you some of the drawing things you can work on, I hope it helps :)

So - I'm no expert by any means - but what strikes me is how good your light/shadow relationship is on the back of the scarf (the dangly bit), but how you have not carried this through onto the face - the shadow on the blue bit of the scarf reads ok, but you need more contrast on the shadow side of the face and around the eyes and down the nose - this will start to make the face and head look the right shape... You've done a good job with the colours though - pretty good start I would say :)