I need help to understand some grammar in this sentence

何度ゃったって
結果は同じだ
それが世界の真理なんだ

So I translated it for "no matter how many times I will try, the result will be the same. that's the truth of this world"

But there are two things that I don't understand here:

1. ゃったって? where it came from? te iru form of やる (to do)? Because I know there is どうゃったって - what do you saying

2. なんだ? is that to explain ton or something?

Thanks, Or