This arrangement works much better, but some adjustments are needed to make it work. First, the fireplace grouping needs to be tightened. It crowds the dining area and you need a passageway behind the couch. Turn the rug lengthwise, parallel to the fireplace. Pull the large couch about 2 1/2 feet closer to the fireplace, and place the two chairs and loveseat on the ends of the rug, and pull them closer together. This will give you a more intimate conversation area, and not impose on the other areas of the room. Remove that floor lamp from behind the couch. If you need the light in that area, put it by the fireplace. Also, the stereo system on the mantel needs to find another home. Maybe it can go IN the fireplace instead. At the other end of the room, I think the arrangement would look better if the seating were rotated 90 degrees. Keep the rug and coffee table in its current configuration, place the sofa either facing the window or with its back to the window, and put the two chairs opposite it. Finally, the dining area. Now that you've moved the big leather chairs, you should have enough room. Your rug is too small. It should be big enough to give you at least a 2 ft. border all the way around when the chairs are pushed in. And it's a really beautiful table; please uncover it. I can't see what kind of lighting that area has. It really needs a pendant or chandelier hanging directly over the table.

Scope of work would benefit from consulting an architect.

that is what i have added if you can see the pic above.. want some suggestions on partition that i can use between dining and sitting

Just because you want to use the space below the stairs, do not just add drawers or shelfs unless you reaalllyyy need it. I would suggest go for adding something green to your house. Its healthy by adding air purifying plants. These plants are nowadays available in most of the nurseries and moreover Green patch in the house gives a beautiful look to the house and is also good for eyes ( the green color). Below are few picture to motivate you for Green patch or Indoor garden.