How to repair short circuit in my phone

You definitely shouldn't charge phone (or even try to turn it on) that was in water or any liquid. Normally you should do as in this guide (it's for iPhone but general points works for all electronics).

If I understand correctly, charging port on a phone melted? There is no easy solution for that, this phone does not have charging port detached to mainboard, you cannot just replace it. I don't think this is salvageable situation, but maybe if you open it up and clean it, it will work? But I doubt it.