How to write sum formula in google excel?

Question

Google

I am preparing a table with project data and the pivot table should count the number of days for given conditions from another sheet and the sum of days.
Given 4 excel sheets
3 projects + pivot table
In the project table there is a page complexity column with selection options, for example "complex" and "simple", in the pivot table you need to count the number of these pages and how many days they can be done ... is this possible?
Pivot

Table Project Table

Answer 1

IMHO, simple formulas COUNTIF and COUNTIFS will help with your task