For me improvement just came by playing lots of games
Blitz
I am not bad at rapid (1100)
I am not bad at daily (1000)
I am not bad at bullet (1000)
but I suck at blitz (800) , why ? why is blitz different from other time ranges for me ? and how can I improve ?
Rapid ratings are inflated compared to blitz ratings. You are not worse at blitz than at rapid. Here is a site where there is a lot of data for comparing blitz and rapid ratings https://www.chessratingcomparison.com/Graphs
Focus on one time control you want to be good at.
If you play a faster time control, then you lose on time.
If you play a slower time control, then you play too superficial and lose on the board.