Is it permissible for the Mudarib (investor/manager) to take a monthly salary from the capital, if the Mudarabah company has not made profits for two years, knowing that the capital owner has agreed to that?

It is not permissible for either the mudarib (agent/worker) or the Rabb al-Mal (capital provider) to stipulate a fixed salary for themselves. They are only entitled to their agreed-upon share of the profit, if profit occurs. The mudaraba contract becomes invalid if one of them stipulates a fixed sum of money for himself, because this could lead to one of them taking the entire profit or a portion of the capital. Furthermore, it is essential to specify the worker's share in proportions (e.g., a percentage), because stipulating a fixed sum of money could lead to the worker becoming lax in seeking profit. If the mudaraba contract is invalidated, the profit and loss belong to the Rabb al-Mal, and the worker is entitled to ajr al-mithl (a reasonable wage for similar work). However, if the amount given to the mudarib is a loan until profits are realized, then there is no objection. Alternatively, the mudaraba contract can be dissolved, and a lease contract (ijara) can be established between the capital provider and the worker for a known wage in exchange for management.