I would like to change my email address and/or password. Is it possible?
You can only change your account email address if you have registered with e-mail (not Facebook or Google account) and have not confirmed your e-mail address yet. If both apply, you can change it in your profile.
Regarding the password, you can reset it if you have registered with e-mail (not Facebook or Google account). Just go to the "Profile" section, and choose "Reset Password". There you can enter your current password and the new password you would like to use. If you do not remember your current password then tap on the "Forgot password?" button instead.
I would like to change my name/gender/age in my profile. Is it possible?
Yes, just go to the "Profile" section, and there you can edit your Name, Age, and Gender information.