Well i thinked that were going to the blockchain funds to pay the core,anyway this reward gets into the new blocks?
Yes.
But the miners dont know that ,they mine a block and get 50 btc or these ammount is bigger because the fees ? Meaning some blocks will give 50,50btc?
Miners know very well how much fee each TX they confirm pays. If they mine TX that pay a total 0.5 BTC fee their reward is 25.5 btc instead of 25 BTC (50 BTC was a long time ago).