why all coins are going down..? can i sale it or hold.
The reason why almost all of them are on a downwards spiral are currently unknown, I have no clue and there isnt any negative rumors about the cryptocurrency world to make all of them to go down in such manner.
A drop in bitcoin prices could cause investors to lose confidence in bitcoin, a drop in funding for bitcoin start-ups, and a wave of large-scale closures by some bitcoin start-ups, eventually creating a vicious cycle. These will cause the price to drop.