I generated a btc address and sent the btc to that address, but I wanted to send more so I entered my arch address once more to generate, but now a new BTC address came up, what happens to my old one where I sent my btc?
Nothing, just use the first one everytime! The new one you can leave it with 0 balance. Or you can send money to the new one and it will be the same, you're gonna receive two transaction instead of one.