On generally recognised public holidays, you are entitled to a free day with retention of your monthly income.
If a free day is not possible on a generally recognised public holiday because of work you may be asked to work.
You cannot be required to work on days that are public holidays according to your religion. If you take time off on these days and these days are not a generally recognised public holiday, you have to take holiday hours unless you and your employer opt for another solution. The employer is expected to reasonably cooperate in finding a specific solution for the employee.