Working days in different columns

Hello, guys

Need some help conting working days here.

I have a big database, something like 120K rows (for now) and aprox. 90 columns. Each one of these columns are dates.

Each row represents a client and each column represents a step in his process inside my company. A client don't need to pass through all steps, so some "cells" are blank.

The database looks like this:

Database

I need to count the working days between each 2 columns out of this base.

I've made onother base with working days all the way to 2020:

Columns name (in portugues) are: Date, weekday, tipe (working day or holliday)

I've read some articles teaching how to creat relationship between the working days table and the dates in my main table, but i have so many clumns and i don't know how to create relationship between all of them. 

All i need is a pizza grafic that i can filter by process and see the % wich exceed 2 working days.

Sorry if bad english.