Don't ever feel like you can't post a question here, it's an online Android help forum after all -- no such thing as a stupid question.
Glad to hear you're enjoying your new phone. Just for future reference you might want to bookmark this hardware specs page for your model:
www.gsmarena.com
and this User Manual PDF:
A good way to get familiar with all the things your phone can do is to sit down and go through the Settings menu. There are a lot of features and options that allow you to customize and optimize your phone to suit your own personal preferences. It's a bit overwhelming so just take in things at a pace you're comfortable with. And keep in mind there are lot of sub-menus and contextual options that may not be in plain sight. A lot of them are accessible by a gear icon, three horizontal bars icon (a.k.a hamburger menu), or three vertical dots icon. Don't make too many alterations at once, keep track of what you do change so just in case that creates a problem you just need to go back and restore that option.
You'll eventually want to do the same with the apps you do choose to rely upon. Don't expect the default settings to always be to your advantage, go into each app's Settings/Options/Preferences menu and set up your chosen apps to work for you, not what some developer thinks is best for you.
As for phone calling and voicemail you can just use the default Phone app. It will interact with your account with your cellular service. There's also a default text messaging app that will do the same. There are a number of third-party apps you might prefer but for now you should just get used to what's already installed and then look into alternatives if you find the default apps to be lacking in some way. A lot of third-party apps will have more user-adjustable features and options. Again, don't forget to look in Settings menu of your apps, there could already be options to alter or enable to make an app work better for you.
