Did Jesus ever said that he is going to die for your sins?

are good people equal to bad people? aren't everyone responsible on their sins the have commited and should seek repentance and forgiveness? does that mean you can do anything you wish to do since your sins were erased? is this really what Christianity is all about, which is about salvation, die on the cross, die for our sins? or is it really about the 10 commandments. how can you say God is three while he never said he was three and insist that He is only one! how can you insist that Jesus and God are the same while in many verses it shows that they are not. "my God my God why haven you forsaken me?". does the word "son" in the Bible really means son as we understand today, or it means a follower worshiper?