is there have instant buy/sell button I could use? when the market moves quickly I can't react quick enough due to price quickly changed.
You can just buy at 5% higher price than current, and sell at 5% lower price than current.
It is equal to open Market order and you will get best price possible.
it's hard because when I need instant order I know the market is going to move quick, setting 5% each time isn't an option.