Workforce-based production plan - something like Gantt chart

Good morning everyone,

I have a difficult problem and I do not know how to solve it. I do not even know in which direction to go, what formulas I should use?

Assumptions:

1. In the first step is planned the number of employees. It is planned for each employee which day he is in the plant and how many hours he works.
Let's say the range is from 0 to 8. Zero means a day off.
The plan can be expressed in hours per day or better with an indication of the hours the employee is working.

2. Orders are entered with the exact number of hours for each task with detailed hours for each department. Workers 1 and 2 work in the department 1 and worker nr. 3 is employed in department 2.

3. Production is planned. It looks like a Gantt diagram:
- orders are selected from the list of entered orders
- Diagram takes into account when an employee is at work (or when he or she is absent), and counts the number of planning hours.
- the second department can not start work (step2) until the first department has not finished the task (step1)
- If the order is not completed in a current week, on the right side ( AQ column) will arise the remaining number of hours. This hours can be rewritten on the production plan for the next week.
- if the employee is assigned to two tasks (or more), then the implementation of course is one by one.

Does anyone have an idea how to solve this task? Which formulas to use? For all help I would be grateful

Best regards,
Daniel