Bullet Chess... How do you improve?

Nobody has time for improvement with bullet chess. Just play. Rating goes up and down, up and down. If you have some kind of a goal with your rating, just make sure to stop when you are at that goal.

I feel that most of my bullet games end and I am just like....wtf just happened lol. Anyway, improvement requires familiarity with many positions, especially the opening moves where you should take almost no time. Do not put too much stock in your bullet rating though, it should be just good fun.

Bullet/blitz chess I feel is a test of what you are able to currently do positionally and tactically...so I'd say improve in regular play and chances are you'll also improve in bullet/blitz.
Just starting playing some Crazy house... it the best form of chess in my opinion
is there on line crazy house?
yes, on fics and better yet, en.lichess.org