Is purchasing goods in installments a legitimate transaction if the invoice separates the cash price from the credit charges, and should the cash price, the installment price, and the installment value have been stipulated?

There is no harm in transacting the sale of goods by installments, as long as the price is known and specified, and the amount of each installment is also known. Furthermore, no increase should be stipulated in case of late payment. The amount of credit fees or the lack of differentiation between immediate payment and installment payment does not affect the validity of this transaction. What matters is the determination of the goods' price and the execution of the contract based on it. If the fourth hundred in the contract refers to credit fees, and the intention behind it is insurance on the debt and its stipulation, then there is no harm in it if it is cooperative insurance and not commercial.