How to get to Total Percentage of values that are based on other totals and values

Question

example:

Main Goal : 100%

Specific Goal 1 : 40%
Task 1 : 40%
Task 2 : 30%
Task 3 : 30%

Specific Goal 2 : 20%
Task 1 : 20%
Task 2 : 50%
Task 3 : 15%
Task 4