To take a screenshot on an Samsung Duos GT-S6802 phone, you must press the Power key and the Volume down button at the same time.
For Samsung phones, there is an original way to take a screenshot, this is to hold the edge of your hand across the phone screen from left to right.
As a result, the screenshot will be placed in the gallery. After that, you can use the image to share it on social networks, instant messengers, or keep it as a photo.