Hitler originally wanted Jewish people to leave Germany. It was only when that failed that they instituted death camps. That's why it was called the final solution.
I haven't used Brilliant a ton but I don't think the other poster has used Brilliant at all. I've seen zero videos in any lessons I began. Maybe they're thinking of Khan Academy.
Most reinfection studies were done on people who contacted it more than once in a year IIRC, and COVID suppresses T cell levels for nearly a year, or sometimes even more.
I'm not sure we can say more infections = higher risk per infection, but each additional infection is another roll of the dice in any case.