I'd wanna learn Psycology.
If I could learn to do ANYTHING?
I'd learn to freeze anything upon command or shoot electricity through my fingers. Hehe.
Seriously though, I'd invest a whole bunch of time to learn how being a cure researcher is. That type of thing has always interested me, and I want to be in the place of a cure researcher - a type of job that is doing humanity a favor for not only the current generation, but also future generations.