If you don't understand the existing language, you can do by seeing the icon of each step as I will show below.
To go to the language setting menu in Samsung Galaxy S5 (also for other devices using Android 4.4/ Kitkat) :
1. From main display, choose and tap/click the Apps icon
2. Then tap the Setting icon
3. Choose the 3rd row, that is the Sound and Display menu, tap the V icon to expand the menu
4. Now you can see the A icon, that is the language and input menu
5. Here is the menu for change the language
6. Choose and tap the new language you want to set.
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Good Luck.