The best person I have found to really understand Facebook Ads from a numbers standpoint (and success rate) is Gabriel St. Germain.

https://www.youtube.com/c/gabrielstgermain

His channel focuses on e-commerce strategies, but gives you the nuts and bolts of understanding the backend to Facebook ads to really understand if you are targeting your customer successfully and gathering the proper metrics for your campaigns.

Let me know if you have any further questions!
Justin