Is money earned from working as a sound engineer in the Ministry of Culture, which includes permissible and impermissible tasks, considered halal or haram, and must one dispose of it, and how does one repent from this mixed money?

Sound engineering for prohibited activities, such as musical concerts, is forbidden because it involves assisting in sin. Salaries earned from a job that includes both permissible and forbidden tasks are not entirely forbidden; rather, what is forbidden is only the portion corresponding to the work done in the forbidden activities. This portion must be disposed of. If it cannot be precisely determined, it should be estimated based on the most probable assumption. As for the profits from trade made with those salaries, they are rightfully yours.