Is he considered sinful, the one who buys a computer for his friend using his credit card, in return for receiving the interest amount added to the price of the device, with the aim of helping his friend avoid the complicated procedures of buying it in installments?

It is permissible to use a Visa card that is free from Sharia prohibitions. It is permissible for the cardholder to buy an item and sell it to his friend in installments at a higher price, provided that he first owns the item and the contract is made between them. It is not permissible for the cardholder to lend his friend the price of the item to be returned with an increase, as this is forbidden usury (riba).