I’m actually really confused with the whole story. I don’t get it, can someone explain it to me
It may be confusing if you haven't read Rumspringa no Joukei, because It's like a spinoff. Otherwise it's pretty simple: Trevor's nephew, who is called Gene, comes to him to clean his office and finds a diary where Trevor wrote about the time he spent with a man named Gene (the amish Gene, not the nephew). So the first part of the first chapter basically gives a frame to the main story about Trevor and the amish Gene. We get to "hear" the story as the nephew Gene reads it from the diary.
I don’t know where this story actually goes. But either way I love it