How do i develop extreme resilience to diseases?

Not in real life: Heroes in fantasy fiction enjoy immunity to disease, but no human being can do this. You can improve your chances of staying healthy by eating sensibly, staying physically fit, being immunized, and getting good preventive health care from your physician. But there is no magic beyond this. If there were, the super-rich who know the world's secrets would be doing it -- and they're not. Best wishes.