Sources:
https://www.adameve.com/
https://www.plannedparenthood.org/learn/teens/ask-experts/i-see-on-movies-and-here-people-talking-about-4play-i-wanted-to-know-what-this-meant/
https://sexinfo.soc.ucsb.edu/article/some-culturally-based-differences-sexual-activity/
https://www.expatica.com/de/french-have-most-sex-britsgermans-the-longest-foreplay/
https://www.factretriever.com/foreplay-facts/
https://thechive.com/2018/11/29/facts-about-foreplay-you-should-read-before-your-next-sexual-encounter-15-photos/