Welcome to Android Central! TouchWiz is the Samsung launcher interface. You can install any 3rd party launcher, of which there are many on Google Play Store. Try Google Now Launcher or Nova Launcher.
When you install a launcher it should ask you which one you want to use as a default. Even just hitting the home button should trigger it to ask you that, then you choose Google.
If you picked TouchWiz, you need to go into the defaults and clear TouchWiz and then hit home and choose Google when it asks.