I feel like with the way I approach my characters, I never think it would be a problem.
Like, I don’t need to have every detail mapped out for the character for things to work, I just need what is a factor in the story. Outside of that they might have other things going on, but since it doesn’t matter to the narrative, I don’t need to think about it.
In this magical scenario where I get to meet my character, they would know more about their own world than I do, the same way I would know more about my own world because I lived in it for a lifetime instead of learning about it from second hand accounts.