Is it permissible to spend a portion of mosque donations on its employees (imam, preacher, and servants), including those who do not have a salary or whose salary is insufficient, or is that not permissible? And what is the solution if the answer is in the negative?

Islam encourages doing good and spending in the cause of Allah. What Muslims donate for the benefit of mosques must be spent for the purpose for which it was collected and in the manner intended by the donors. It should be spent on the mosque's interests as deemed appropriate by those in charge of it, and they are responsible for their trust. The mosque's interests include its maintenance and the wages of those working in it. Therefore, it is permissible to pay a salary from the mosque's donations to someone who does not volunteer their work, or to a needy worker if their salary is insufficient, whether they are an Imam, a Khatib, or a janitor.