Just simultaneously press the home and power button to take a screen shot. This feature is quite good actually. You can do the screenshot while opening videos, files , and browsers. After you have taken the screen shot, there will be a notification on your upper left corner screen...it's like an image icon. Hope this help.
To know if ever your phone is original or fake just check the imei
Go to your dial pad and type *#06# and get the imei and check your imei in the imei checker in the google and see it if your phone manufacturer is that brand or not
Need to capture what's on the screen? But your phone didn't have any physical button ?You can take a screen shoot by downloading a certain app called "Screenshot Easy". Here's the external download link (Not from the Playstore but safe) : https://screenshot-easy.en.uptodown.com/android. Just open the app and take a screen shoot . I hope it will help.