SO I replayed the game as you suggested. And this time, I reached the Godot boss everyone was talking about ! Yay ! I'm pretty sure the candle wasn't there the previous time, or it didn't do what it did this time ! But indeed I was able to progress. I still felt very slow. Also during the boss, I noticed that some ghost were stacking on top of each other (when I would stay on the left so they would spawn), so during the boss battle, when touching the ghost I was taking a point of damage for each (I had 3 stacked). I think I was testing a bit the limits there ^^