Serious Chess
Learn and apply the most important principles of chess.
Always blunder-check your moves.
Solve tactics in the right way.
Analyze your games.
Study games of strong players.
Learn how to be more psychologically resilient.
Work on your time management skills.
Get a coach if you can.
Just one piece of advice (I am sure you'll have more in this thread). Your puzzle success rate is only 55%. That's way too low. It means you do not calculate all relevant lines and do not try to find all the best defense moves for your opponent. You should shoot for at least 75% success rate, preferably higher.