If there is duality, at the big bang, when matter and antimatter was created, why did the balance shift to matter? Someone told me that there is a theory that the particles that have no charge was left over and created matter?
Take a look to the wikipedia entry about baryogenesis. To create this disbalance between matter and antimatter some conditions (called Sakharov conditions) are needed. The standard model of particle physics explains at least partially how these conditions might have taken place, but there is still no conclusive theory about matter antimatter asymmetry.
i also heard an idea that, if their was an event horizon at the big bang, and an antiparticle- particle pair were next to it yet only the antiparticle was in it, then the particle would survive and become a real particle