Is the amount taken from a friend in exchange for a fixed monthly profit considered usury (riba)?

The Mudarabah company (partnership) is when one person gives his money to another to trade with it, and the profit is shared between them according to their agreement. For it to be permissible, the profits must be a known percentage of the profit, such as half or a third. It is not permissible for it to be a known percentage of the capital, such as 10% monthly from it, nor a known amount of dirhams, such as 1000 dirhams monthly. If any of these conditions are stipulated, the contract is invalid and unlawful by the consensus of scholars.