living vs existence

living and existence both are nouns.

Word	Noun	Adjective	Verb	Adverb
living	Yes	Yes	No	No
existence	Yes	No	No	No

As nouns, existence is a hypernym of living; that is, existence is a word with a broader meaning than living:

Other hypernyms of living include being, beingness, face of the earth.

living (noun)	existence (noun)
the experience of being alive; the course of human events and activities	everything that exists anywhere
people who are still living	the state or fact of existing
the financial means whereby one lives
the condition of living or the state of being alive

living (adjective)	existence (adjective)
pertaining to living persons
(informal) absolute
still in existence
(used of minerals or stone) in its natural state and place; not mined or quarried
true to life; lifelike
still in active use