Change email: open Settings, then Account, then Email, enter the new address and confirm using the link we send to it.
Reset password: on the sign-in screen tap Forgot password, enter your email and follow the link we send. If no message arrives, check spam and make sure you used the email of your account.
If you no longer have access to your email, contact support from another address and explain which account is yours. We may ask for proof before changing anything.