The tutorial thing is sadly a bug, we will fix it post jam. But if you say no to the tutorial before you fully start the game (when you first run the game), it shouldn't keep reappearing after each boss.
But you did well the idea is to use the dash to sync yourself up before switching to an attack or rewind, helping you to maintain the beat.
You have 3 combos one focused on damage which should help you to beat the boss faster, another heals you and the other gives you a shield. You discharge the reel to use them. It has a bit of a learning curve but Im glad you enjoyed it! Thanks for playing our game <3
Ps. Once you do get into the game and you sync your attacks and different combos to the music its a great feeling! :D