For which part? Do you have a Facebook account? It's not exactly a secret.

Any sources for any part will do.

Although, the whole "They have people who's sole job is to make sure Facebook users are on the platform for as long as humanly possible" part makes me the most skeptical.

Sean Parker on maximizing engagement: https://slate.com/articles/technology/technology/2017/11/fac...

Psychologists running studies on users: https://www.forbes.com/sites/kashmirhill/2014/06/28/facebook...

Then of course there's this guy: https://theguardian.com/news/2018/mar/18/facebook-cambridge-...