Inorder to get your correct firmware you'll need to identify your device model in about phone as you'll need to select in the drop box and you'll also need to know your device csc as these are key to downloading the correct firmware (to find your csc, boot your device into download, the three letters under the heading carrier are your csc)
Once done use the 2 on the 2 boxes provided and click check firmware, it will take you to the firmware, download the latest.
Now you'll also need to download Odin also from there... also go to https://www.samsung.com and download the latest samsung usb driver
Once you are here get in touch and I'll walk you through the next steps....
If you bought a 2nd hand phone, you might have to leave that alone bro. Because that one might be locked due to unfinished monthly installments. Now to bypass KG Lock and knox that is one way of doing it. You remove that and the phone locks you out
