I wrote a novel and it is Science fiction based novel. Almost every close friend of mine read the novel and none of them gave a negative response. What are the possibilities that I need to assume, which can make my book bestselling.
A lot of factors collide to make a book a bestseller. It's not just the writing - there's also how original the concept is, and how much it speaks to the audience, the right place, the right time, and probably more. The same book might not have sold as well had it been published a few years earlier or a few years later. Or it might have sold just as well.
Having a bestseller is a surprise. Don't plan for it. Don't expect it. It is a rare thing. If it happens, enjoy the ride while it lasts.
The only exception is famous authors who have already written multiple bestsellers: they can reasonably expect their name alone to sell many books. Although, even a famous author's book can flop. It's just that after you've written several bestsellers, your financial future doesn't depend so very heavily on the next book: it will sell enough even if it isn't a bestseller, and there are the royalties for the other books, and you'll be already writing the next one by the time this one is published.
A final note: you say your close friends read your novel. Have you considered the possibility they don't want to give you harsh criticism? Or their perception of your novel is coloured by their friendship with you? Or, being your friends, they like the same thing you do, which might not be the same things a larger chunk of the public would like? Trust your friends' criticism. Be wary in accepting their praise.