How to use If else statement to create burst report for performance review?

I have a real industry problem with the employee work performance report. In the table, we have the data items as follows:

EmpName EmpDue  ManagerDue  Manager2Due  ReviewStatus  SubStatus
   A  11/05/19   11/12/19    11/19/19    Not Started   EmployeeAssessment
   B  11/19/19   11/26/19    12/3/19     Not Started   EmployeeAssessment
   C  11/01/19   11/08/19    11/15/19    In Progress   Manager Assessment
   D  11/01/19   11/08/19    11/15/19    In Progress   Manager2 Acknowledgement
   E  10/3/19    10/10/19    10/17/19    Completed     

So, if the Review Status is Not Started, and Sub Status is EmployeeAssessment, it means, the employee himself has not started to review himself.

Expected Result:

We would like to send out the reminder 7 days before the employee's due date. If the employee doesn't take any action and the due day passed, then we would like to send out the reminder every 3 days(which means 3, 6, 9...) after the due date.

Once the employee reviewed himself, then it comes to the next stage, which means the ReviewStatus will change to In Progress, and the sub status will be Manager Assessment. At this point, we would like the direct manager to review the employee. If the manager didn't do so and the manager due date passed, then we also would like to send out the reminder every 3 days.

After the employee and manager did the review, then it turns to the manager2 to review. the Review status will still be In Progress,the sub Status will be Manager2 Acknowledgement, the same reminder will send out to manager2.

After all the people completed, then the review status will become Completed.

Due to the real working platform, I don't know how to apply if-else statements in this case, especially for the 3 days rotation.