My iPhone wont turn on or won't let me charge and overheats

so i dropped my phone down the toilet and sent it off for repair, i got it back weeks later and it worked but then my friend was taking a video in the rain and my phone froze so i put it in a warm place and it came on. After that it kept over heating and loosing charge really quick, also taking ages to charge. So i was charging it and took it off, it was really hot and burnt me (it came up with the temperature triangle like it always does) so i turned it off, now it won't turn on or charge. I've tried pressing the home buttons and that but it still won't turn on. How can i fix this?