hikaru said this and I completely agree: beginners (800-2000 elo) are bad cuz they just blunder shit for no reason, the complex deep strategical stuff matters very little if you blunder your rook in the 15th move. what I recommend is playing a lot of puzzles, then going to longer time control (at least rapid) and consciously being very careful of each move, trying to see if you are not blundering anything. you can start learning opening and endgames later.