The developer is a general contractor who is responsible for the construction of a building. He usually has the building built by subcontractors and then sells it together with the property to a buyer.
The basis for a solid building result is a detailed building description that includes all services and materials as well as their prices. Make sure that this description is complete, as the developer is only obliged to provide the services contained in the contract.
As a rule, a fixed price is negotiated with the developer. Check carefully which services are included in this fixed price in order to avoid unpleasant surprises later. This is the only way you can guarantee risk-free and smooth real estate financing and prevent avoidable refinancing.