Is it considered usury for one person to take money from another to trade with it, on the condition that the original amount be returned to him with an agreed-upon increase (for example: taking 400 and returning 450), knowing that the owner of the money is not a partner in the profits or losses? And what is the ruling on the creditor and the debtor in this case?

This contract is invalid because it includes an increase in the loan, which is the prohibited usury of the pre-Islamic era (Jahiliyyah). Therefore, the amount taken must be returned without increase or decrease, based on the Almighty's saying: "And if you repent, you may have your principal - [thus] you do no wrong, nor are you wronged," and the Prophet's (peace be upon him) saying: "Whoever increases or seeks an increase has engaged in usury; the one who takes and the one who gives are equal."