I'm looking for a story where a person is a participant in a cultural exchange. For example, when humanity entered into diplomatic relations with Equestria (or any other country on Equus) and a person was sent to them so that he would learn their culture and study.

A long time ago I read a similar story, but over time I lost it

https://www.fimfiction.net/story/519021/equestrian-reformation maybe?

kind of sounds a bit like "Project Sunflower" but other than that one I haven't seen any stories like that (that I can recall coming across that is)

https://www.fimfiction.net/story/447159/the-embassy