To count the number of working days, you can use the NETWORKDAYS Function, which returns the number of whole working days between two dates.
=NETWORKDAYS(A2,B2)
Where A2 is the start date and B2 is the end date.
If there are holidays between the two dates, you can remove them using the formula below:
=NETWORKDAYS(A2,B2,C9:C12)
Where A2 is the start date and B2 is the end date. C9:C12 are the holidays.