Is the transactions in one block effect the hash of the next block? How?
What i'm asking is, does the contents -transactions- of one block effect the hash of the next block? if so, how it happens?


Yes. The block hash of block X is explicitly included in the header of block X+1. So if you change the transactions in block X, it will affect the hash of block X, and that would change block X +1 as well. 


  For example, lets say that we mined 10 blocks. Then, we hacked block number 5 and changed the transactions.


The nodes on the network that already know about block 10 would not accept your new block 5 because it is a shorter chain (less work than the chain that is at block 10). They can recognize the new block 5 as being altered because the longer chain does not include it.