First home Gurugram: Hidden costs & negotiation confusion

₹1.8 Cr for a 3BHK in Sector 95A, Adani Realty ka project dekh raha hoon. Builders bolte hain price fixed hai, but Gurugram mein negotiation kitna possible hai? Matlab, kitna knock off kar sakte hain? Aur possession ke time kaun se hidden charges aate hain? I'm worried about total all-in cost, not just basic price.