If the second guy is lying, that means we know the two liars and the third must be Life. But he says he isn't. Therefore, the second knight is Life, the third is Dungeon, and the first is Death.
But solving a puzzle isn't genius. It's logic. Some people spend much more time with logic than others: programmers have lots of games like these. The Blue Eyes puzzle comes to mind as a particularly hard one. Similarly, the more people program, the more they learn mental shortcuts that let them be more productive. Time fixes everything, and the best attribute to fix things is passion. You've got that. You just need to make sure to unfailingly look for whatever your goal is, and to learn everything you need to pursue it. Remember: there's more to building something than programming.