Buying a house from a developer: Is an expert necessary?

All houses will / are supposed to be finished by the end of March.

Then it is hardly worth it now.

As I said, the relationship to the developer

The developer sells you a piece of a house. Legally, neither you nor the expert are allowed on the construction site. There is also no right to defect rectification during the construction phase; defects are only recorded upon handover (it's like when buying a car – you are not allowed to go into the factory with a car expert to check whether the car is being built correctly. Only after handover can you identify and have defects remedied). Nevertheless, it is not bad if you and an expert are allowed on the construction site. Then directly now and for 1x.