I'm not sure specifically as I haven't read this particular fanfic. But generally, it might be about the relationship and adventures of Gohan and Pan in a fictional and perhaps creative or alternative storyline created by the fanfic writer.
In some fanfictions, Gohan and Goku might have a series of conversations that open up new levels of understanding between them. Gohan could share his thoughts and feelings about his life and future, and Goku would listen and offer his own insights. This kind of communication can really strengthen their bond.
In such fanfictions, Goku might develop by becoming more of a mentor to Gohan. He could teach Gohan new fighting moves and also how to control his emotions better during battles.
In a Gohan x Goku fanfic, their relationship can be delved into by creating scenarios where they have to rely on each other completely. For example, if they are in a situation where Goku's strength and Gohan's intelligence are both required to escape. Their different personalities can also be highlighted. Goku's carefree nature contrasted with Gohan's more studious and responsible side. And of course, flashbacks to Gohan's childhood and how Goku's presence or absence affected him can add depth to their relationship.
A Goku Reader Pan Fanfic usually centers around the relationship between Goku and Pan in a fictional scenario. It could be a romantic relationship, a mentorship kind of thing, or just a friendship. The 'reader' part might mean it's written in a way that makes the reader feel like they are part of the story, experiencing the events along with the characters.
Well, 'goku x gohan lemon fanfic' could potentially be a fanfic that focuses on the relationship between Goku and Gohan in a more creative and perhaps emotional way. It might explore their bond, their growth together, or some fictional adventures they go on. But the 'lemon' part could also imply that it has some sort of romantic or affectionate undertones, though this is just speculation.
One possible interaction is that Bardock could spar with Goku and Gohan. He'd test their limits and see how much they've learned about fighting. Another could be Bardock sharing stories of Planet Vegeta with them, which would be really interesting for Goku and Gohan to hear.
In the manga, Gohan never managed to defeat Goku. Their battles often ended with Goku coming out on top or the fight being interrupted for some reason.
I'm not aware of any such fanfiction. The relationship between Grandpa Gohan and Son Goku in the original story is one of love and mentorship, so this kind of dark and negative portrayal in fanfiction is not common that I know of.
You can focus on their emotional bond. For example, show how Goku's pride in Gohan's growth and achievements affects their relationship. It could be about Gohan seeking Goku's approval and Goku being there to give it wholeheartedly.