Hi Monika, first off you've got some great architecture in your space, that stairway is the focal point in the space and I think you'd do yourself a great service in treating it as such. Painting it a darker tone, like
http://www.benjaminmoore.com/en-us/paint-color/nightingale
You already have those tones on your sofa and large wall art, hutch and floor carpet.
I would wrap the rounded stairwell feature and as well as in the back wall of the dining area.
You have a lot of nice pieces, it's the proportions that are wrong. For example, your light in the dining area is too small for the space. I say research Scandinavian chandeliers on line and find one you like, I'm offering up an example.
layer your curtains, a nice white sheer to filter the light with a darker heaver curtain in a gray or even olive/green color to coordinate with your chairs would be lovely. You have the right idea with hanging your curtains to the ceiling.
Hang a large mirror over your gray console and move the smaller storage furniture out of the dining area- it ages the space. You could hang a tall framed image on either side of your glass cabinet. Coordinate the frames to wood on the glass cabinet .
I agree that you should bring some of the green into the rest of the room, throw pillows and new art would help do that.
Hope that helps.