Looks like your fireplace stone has a grey green colour with accents of charcoal and pinky rust. Looks like your sofa has a pink or yellow beige undertone. Hard to tell what colour your walls are, but I would suggest the sofa be more greige or grey. You could bring in blues or charcoals and creams.

You could accent with cream, orange and blue or charcoal

my walls are cream

second my fire place has light brown, grey and dark brown tones

can I go for a beige sofa?

this is sofa we choose

As long as you choose a rug that allows the beige sofa sectional stand out. It will be the color closest to the sofa as opposed to the walls. To answer your rug question, I would pick a bolder accent color that you will be happy with. Like the colors mentioned above, blues and charcoals would be good.

In that case I would choose a light grey (bluish grey) rug. You do have that color in the fireplace.

It's too big

my room is 18ft x 18ft

while the sofa is ... 141 inches by 110 inches

will that be too big too?

Depending on the orientation, that leaves about 11 3/4 feet of room on both sides. If you plan to use side tables, that leaves you too little room to walk ( maybe 3 feet) on one side of the sectional let alone an accent chair. Have you taped out the sectional in the room? If you aren't convinced, try taping some newspaper together to create the footprint of the sectional. This way you get the sense of mass as well.

i taped it

ok ... will do the newpaper thing