Anyways, if you're a newer player and want to improve your game fast, this is what I would focus on.
1. Tactics. The vast majority of games between newer players are decided by tactics...someone hanging a piece, falling into a trap, etc. Practice tactics by doing puzzles, reviewing games of strong players with tactical themes. Lichess and Chess.com both have decent collections of tactics puzzles.
2. Don't try to learn a ton of openings. Pick one or two openings for white and black, and focus on them. Don't try to memorize lines, but rather become more familiar with the structures that result out of the openings, what typical objectives for white and black are, etc.
3. Familiarize yourself with endgame play. This is less important than #1 as a newer player, because all the endgame knowledge in the world means nothing if you hang a rook in the first 15 moves. But, it IS still important though, because you will get into endgames with a small advantage (or disadvantage) so you need to be familiar with how to convert that into a win (or hold your position). Rook endgames are especially important since they are generally the most common type of endgame. Lev Alburt has a good book called "Just the Facts" which covers endgame play. There are also puzzles and excercises on lichess and chess.com
4. Probably the fastest way to improve is to actually play games against stronger players than you and have them analyzed or annotated. You can either do this with a computer program, or a stronger human player if youre fortunate enough to know a strong player or have a coach. Lichess and Chess.com both have tools which will analyze your game and point out mistakes, missed opportunities etc. These are very helpful, they will instantly point out key moments in the game so you can see where you (or your opponent) went wrong.
Improvement in chess is really a volume game. The strongest players have played thousands of games and have a good sense and understanding of different positions because they have seen so many of them. They're able to quickly recognize patterns in these positions and devise a plan based on strengths/weaknesses. The best way to sort of develop this sixth sense is to put in the volume and play!