How to change the Soft Button layout in Samsung Galaxy S8+(SM-G955)?

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Navigate to Apps → Settings → Display → Navigation bar → Button Layout → Recents-Home-Back

Pictorial representation of the above settings are as follows : 

a). From home screen, swipe up to launch Apps.

b). Tap Settings.

c). Tap Display.

d). Scroll up the screen.

e). Tap Navigation bar.

f). Tap Button layout.

g). Tap Recent - Home - Back.