Is it permissible to reclaim half the purchase value of the kitchen in the form of bank certificates after six years, according to the company's offer?

This contract is impermissible because it involves stipulating a gift within a sales contract. This is due to the prohibition of "a sale and a loan" (بيع وسلف) and "two sales in one" (بيعتين في بيعة), and because this condition contradicts the very nature of the contract. Furthermore, the aforementioned gift consists of usurious bank certificates, and usury is one of the gravest major sins.