Is it permissible to receive a fixed monthly salary from a government bank in exchange for depositing a compensation amount with them, knowing that the salary is calculated on the basis of an 11% interest rate?

The bank is not considered a means of halal (definition) investment unless it adheres to the provisions of Islamic Sharia (definition). The early retirement scheme offered by some banks is forbidden usury (riba), and it is not permissible to benefit from its returns. Placing money in the bank in exchange for a monthly salary is a loan to the bank, as you can recover the full capital. Some may think that the bank invests the deposited money, but this is incorrect, as the bank prefers lending to avoid risks. Even if the bank were to invest, specifying a predetermined percentage of profit from the capital is not permissible, because it might earn a lot and give a small percentage to the owner of the money, or it might not earn anything or even incur a loss. Therefore, it is best to resort to investment methods known in Sharia, or to deposit the money in an Islamic bank if you cannot find a way to invest it yourself.