Someone wanted to learn this too, so Grasp built them a personal learning path.
You can keep exploring this one or create a path like this one shaped around you.
Recommended resources
Module 1
Audit Framework & Preparation
Module 2
Tracking & Measurement Integrity Audit
Module 3
Funnel & High-Level Performance Analysis
Module 4
Account Structure & Hygiene Audit
Module 5
Audience Strategy Audit
Module 6
Creative & Messaging Performance Audit
Module 8