Sorry for all your problems, I have a 6s and haven't had these issues. You can always make an appointment with the apple store to gets these issues checked out. For the battery, I'd recommend checking out the energy saver tips on apple such as turning off background app refresh in the settings;
Batteries - Maximizing Performance - Apple. Setting up the email server can be difficult, especially for some email companies. Checkout the guide posted on your email vendors website or other online source. Not sure what to do about the sound other than getting apple to take a look at it. Hope things workout for you.