why

i play 15 min games and i have 1800 but i got only 1400 in 1 min game im slow player anyway to improve in 1 min

Because your standard rating is so much higher you're probably thinking too much.  Need to set the bar much lower for your moves, it doesn't even matter if you think of them as mistakes, the only criteria is they don't lose immediately to a tactic.  Keep your pieces coordinated and do what you usually do out of the opening, but never analyze and just play OK moves as fast as you can.  That's where you need to start at least.  Once you adjust to the speed you can pick times to think a bit.  At first though I'd just practice moving nearly instantly and see how far you can get.

For example if there's a complicated tactic / series of forcing moves to do to your opponent, don't analyze it, just do it.  If you can spot it and execute it faster than they can then you gain time on the clock.  In a 1/0 game you may end up a piece down because of that series of moves, but if you're 15 seconds up then you're more or less winning if you can keep pace with them the rest of the game.

Yeah, I played 10 minute blitz so that I'd have time to think about my moves and learn to play on a deeper level for a long time, but after switching to 5 minute (since that seems to be the standard at my local club) my blitz rating took a 100+ point nosedive and has yet to recover.