Practice, puzzles, tutorials, and overall just enjoy and play the game.
How do I improve?

Hi there,
I am rated over 2400 online (https://www.chess.com/member/ppandachess). I created a free course that will teach you a training plan to improve. Feel free to check it out: https://www.panda-chess.com/daily-improvement-plan
I think that my free training plan can help you.
I also offer private lessons: https://www.panda-chess.com/private-coaching
I am 15, currently around 2100 elo. I struggle playing against higher rated players and I don't know how to improve. I tried solving puzzles and learning new openings but I don't seem to be stronger. I feel like there is a new way of improving starting at 2100. What do you guys recommend to improve? I appriciate all your answers.