(assuming the time traveller cooperates)

Then it depends on whether the future is mutable, or if we’re forced into stable time loops. If time is stable, I’d get some friends. I would never speak to the time traveller directly, but I would text back-and-forth with my friends as they talk to the time traveller. When 3 hours are up, the traveller goes back in time to talk to a different friend in the same three-hour window. (If they’re tired, they can travel back 12 hours and catch some sleep before the next meeting.) It would be an interestingly acausal conversation, but Objective 1 would be finding a more permanent way to bypass the three-hour limit, maybe setting up an AI that will ask good questions of the time traveller. (If they can bring a USB stick with some good AI on it, for instance). We’d also want the future version of Wikipedia, and detailed plans for whatever useful technology gets invented in the future. As well as enough almanac knowledge to get seed money for a future-tech company, and useful news items. I wouldn’t ask about mounting crises like global warming, though, so that my company can do something about it – if I base my actions on knowledge of the future, the future is set. I think.

If the future is truly mutable, though, I just resolve to send a detailed summary of our conversation back in time to a week before I schedule the traveller to come. I get a conversation summary, use it to make the conversation more productive, and then send the new summary back. Repeat until I can take over the world, build a time machine, send a large expedition back to 12,000 BC to do an industrial revolution, and then send an even larger expedition back to the early Universe. When entropy starts to become annoying, go another century before the previous expedition and just accept them as citizens. Repeat until godhood achieved.