But if Satoshi Nakamoto secretly running the Central Server where all the Bitcoin data's are stored then how Bitcoin is decentralised ?
Are you saying that Satoshi may have lied to use and bitcoin is centralized? If so, that's not possible.
Bitcoin is an open-source project and we all know how it is working.
Anyone can download the blockchain and keep a copy of it. Anyone is able to validate transactions. Anyone is able to make a transaction without relying on any third party.