after 2140 the bitcoin cannot be mined
Transaction processing will still occur. New blocks will still be created. There just won't be a block subsidy any more. Instead those creating blocks will get their revenue entirely from transaction fees.
so its mean that no bitcoin left to mine why?
Correct. No new bitcoins will be created after that.
is the algorith set to it?
Yes.
and i want to know that after 2140 the bitcoin worth lower then 1 dollars or will raise from 1000 dollars.. ?
Everybody wants to know that. None of us can predict the future. There are no time traveling machines.