Man, very hard topic to think of. Makes me remember all the great people who are gone now. Also, hard to choose just three. Anyways...
Mr. Alan Rickman, how not to lose your own personality among the so many you have to perform and was it hard to play a villain and then appear in public, knowing most people despise the character you play? Also, is there real Hogwarts out there, now that you're gone, you have to find out EVERYTHING about magical world we muggles know from books only?
Mr. Fidel Castro, how to make people follow you to the very end even though you fail on the way to your goal? People might say it's strong belief in something, but this can't be enough, so what's the secret of being the one changing history?
Mr. David Bowie, I know you're there among the distant stars, is there life on them? Will we ever meet someone not born on Earth or have we already without realising so?
Thank you @missy @rambo