what are the chances of dying while jumping off a two storey building while landing on both feet? Does only some ribs and bones break? Also what if we jumped from a single storey building?

You are likely to break things, but landing on your feet, not likely to die. Really depends on precisely how you land. If you parkour and roll forward, you may not even break anything. If you land with your legs locked, you could break your feet, legs or fuck up your knees, or spine. And so on.