The second floor occupies a large platform, regardless of the property, can I cancel the contract?

Of course. The right to use the platform on the second floor generally belongs to all owners, not one owner. By inquiring about the property official website, we can know that the second floor occupies a large platform, regardless of the property, you can cancel the contract, you can negotiate first, and if negotiation fails, you can sue for rights protection. Individuals cannot directly acquire the ownership of the second floor platform, nor can they arbitrarily occupy the second floor platform.