By default, the Samsung keyboard on Galaxy S7 auto corrects and replaces misspelled words and gives you some prediction texts. To turn off autocorrect on Galaxy S7 (Edge) do as follows:
1. Open the Settings app and find the Language and Input settings and open it
2. Under the list of available input methods, find the Samsung Keyboard and tap to open the keyboard's settings (tap the Gear icon next to it)
3. Now, under the Smart Typing settings, make sure to toggle off the Predictive Text option.
** You can also toggle off the Auto Capitalize and Auto Punctuate options.