English is usually the default keyboard language on Galaxy S7. But you can easily change keyboard language on Galaxy S7, add new languages and switch between them, by doing as follows:
1. Open the Settings app on your S7 (S7 Edge)
2. Scroll down to the Language and Input settings and open it (if you are on the Tab view, it can be found under the My Device tab
3. Make sure the Default Keyboard is set to Samsung Keyboard. Otherwise, tap the Default Keyboard option and select the Samsung Keyboard as the default keyboard.
4. Now, tap to open the Samsung Keyboard settings, under the Keyboard and input preferences.
5. The first option is Input Languages which you should tap the Select Input Languages option under it.
6. Scroll through the list of available languages, and make sure to toggle ON the languages you want to be added to the keyboard language on your S7. (First you need to tap on each language to download it, and then toggle it ON from the list of downloaded keyboards)
7. To switch between keyboard languages on Galaxy S7, simply put your hand on the Space Bar button and slide it over to switch and change keyboard language on Galaxy S7 and Galaxy S7 Edge.