He could have a potions - making adventure. Snape might teach Harry some advanced potions techniques that are not taught at Hogwarts. Or Harry could discover some of Snape's old potions experiments.
In a fanfic, Harry Potter could have many different adventures if he goes to Snape in summer. For example, Snape could take Harry on a journey to an ancient magical site. Along the way, they might face various obstacles like dark wizards or dangerous spells. Harry could also have an adventure in Snape's personal library. There could be books with forbidden magic that Harry is curious about. Snape would have to keep an eye on him to make sure he doesn't get into trouble. And perhaps they would encounter some old friends or enemies of Snape's, which would add more excitement and drama to their time together.
In fanfiction, Harry Potter going to France could lead to an adventure where he gets involved in a mystery related to a powerful French magical artifact. He'd have to team up with local wizards to solve it and in the process learn about the rich history of French magic.
Well, perhaps Snape would be even more surly during the summer. He might assign Harry extra potions work as a form of punishment or to keep him out of trouble. Harry, on the other hand, would probably be more rebellious in a fanfic scenario during summer, as he's away from the strictures of Hogwarts. Maybe he'd try to uncover some secrets about Snape that he suspects.
He could have all sorts of wild adventures! Maybe he'd befriend some magical creatures and help them solve problems.
There could be some old family friends who come to see Harry at the manor. These friends might have known his parents well and can share stories about them. Also, it's possible that he meets some local witches and wizards who are associated with the Potter family. They could offer their help or give him warnings about the upcoming threats. And perhaps there are some magical beings like fairies or sprites that have made the manor's gardens their home and Harry encounters them during his stay.
He could have an adventure in the Spanish wizarding markets. There would be all sorts of strange and wonderful magical items for sale. He might find a unique wand or a potion ingredient that's not available in England.
He could have adventures like exploring uncharted magical islands. Maybe he'd encounter new magical creatures and have to use his wizarding skills to either befriend or fend them off. For example, he might come across a group of mermaids who guard a powerful magical artifact on an island.
Another possibility is that he gets involved in the early days of the Akatsuki. He might try to change the course of the organization, perhaps by convincing some of its members to abandon their more evil plans. Since he's already a retired and experienced ninja, he has a different perspective on things compared to when he was younger.
Perhaps he uses the island as a secret training ground. He could practice advanced spells away from the prying eyes of Hogwarts faculty and students. Harry might also build his own magical fortress on the island for protection and privacy.
They might also embark on a diplomatic mission. With the wizarding world in a state of flux after the war, different magical communities need to be brought together. Harry, as a well - known figure, and Ginny, as a respected witch, could visit other wizarding countries to establish alliances and promote cultural exchange. This would involve meeting different magical customs, dealing with political intrigue, and making new friends and enemies along the way.
They could have an adventure where they have to stop a dark wizard from using magic to take over the non - magical world. Harry uses his magic skills, like casting spells to counter the dark wizard's attacks, while Clint uses his archery skills to take out any minions the wizard has. Another adventure could be finding a magical artifact that has been lost in the non - magical world. Harry has to use his knowledge of magic to track it down, and Clint helps him by using his connections and knowledge of the area.