I’M 600 BLITZ LET’S GOOO!!!

You might not like what I'm about to tell you: You should give zero importance to blitz and improve your level in classical games, strengthening your cognitive connections in chess. When you improve significantly in classical games, start playing 15-minute rapid games. If you improve significantly in classical games, you'll see that when you play blitz, your level will improve dramatically. In reality, at your current level, playing blitz will only stagnate your level or even worsen it.

When you reach a 2000 rating in rapid (and practice with classical games), you'll become a much better blitz player without having to play blitz. If a 2000 rating is too daunting for you, try to reach 1600 in rapid; it's not as difficult as it seems (I've never had to exceed a 1600 rating in my life, but I can't remember anyone I've coached who aimed for an elo lower than 1600 in online chess).

rapid is a bit too long for me :/

You might not like what I'm about to tell you: You should give zero importance to blitz and improve your level in classical games, strengthening your cognitive connections in chess. When you improve significantly in classical games, start playing 15-minute rapid games. If you improve significantly in classical games, you'll see that when you play blitz, your level will improve dramatically. In reality, at your current level, playing blitz will only stagnate your level or even worsen it.

When you reach a 2000 rating in rapid (and practice with classical games), you'll become a much better blitz player without having to play blitz. If a 2000 rating is too daunting for you, try to reach 1600 in rapid; it's not as difficult as it seems (I've never had to exceed a 1600 rating in my life, but I can't remember anyone I've coached who aimed for an elo lower than 1600 in online chess).