Choice of service: if the administrator chooses the performance of a contract that is not or is not fully performed, he assumes the rights and obligations of the debtor arising from the contract. The declaration of the administrator has a future only (ex nunc), that is to say that the service due by the debtor becomes a mass liability and that the service due by the contractor becomes a pre-emptive claim. The contractual conditions initially agreed remain unchanged. Claims of the contractor that were created before the commencement of insolvency proceedings shall not be affected by the choice of the administrator`s performance. Such claims shall be declared as ordinary unsecured insolvency claims. By law, contracts for the rental of immovable property and contracts of employment and services are maintained despite the opening of insolvency proceedings, §108 InsO. . . .