if nobody is mining then there will not be bitcoins generating anymore and verifying bitcoins ? what will happen if there will be nobody in the world to mine. then there will be no future to bitcoin??
and also if nobody is mining then there will not be bitcoins generating anymore and verifying bitcoins ?
Correct. Mining activity has several goals including:


Generating new bitcoins (until 21 million bitcoins).
Verifying new transactions and persisting them in the Bitcoin system (in Bitcoin block-chain).


Mining is crucial for the Bitcoin system and therefore the Bitcoin system provides the incentive (Bitcoin reward) for everybody that participates in mining. The security of Bitcoin is directly dependent to the computing power of network's miners. 

One question that may exist in this context is "Why may miners stop mining?". Miners may stop mining because of a decrease in Bitcoin value. The miners' reward is a constant count of bitcoins (currently 25 bitcoins, which is halved every 4 years). If the value of Bitcoin decreases, the reward for the miners will decrease equivalently, too. 

The worry would be that Bitcoin gets caught in a "Death spiral".


  This leads to the possibility of a death spiral in which loss of
  confidence in Bitcoin could cause the Bitcoin price to go down, a
  falling price lowers the incentive to mine and the equilibrium mining
  rate, lower mining rate leads to the currency being easier to subvert,
  and this leads to a further loss of confidence in the currency.