Chess rush

Practice and keep playing?

Play caro kann for balck, london or blackmar diemer gambit for white and you are fine

And yes, stop playing bullet if you want to improve. Bullet helps you with nothing, you can argue that bullet helps with time management but the truth is that it does not. You only spam illogical moves and hope opponent runs out of time.

Decent openings are very easy to find. All the common ones are at least decent. For example for white Ruy Lopez, The Italian, The Scotch, The Vienna, Queen's Gambit, King's Gambit, London System... They are all decent.

For black you can play symmetrical and respond to E4 with E5 and D4 with D5 or you could play the Caro-Kann or French defense against E4 and King's Indian or Grunfeld against D4. Those are all at least decent.

And there are a whole lot of other openings that are also decent. You could open C4 as white and that is decent also.

Now the thing is, you have to figure out, which of those are the ones that suit your playing style and that you find interesting/fun to play. Then stick with those and improve, little by little, game after game.