How to unroot and remove a custom kernal on android I have had my Samsung s5 mini (G800F) for some time now and am looking to sell it. I rooted the phone and used a custom kernal that allowed OTG support for the phone.

How do I remove the root and the kernal to the absolute original state?

(very simple instructions would be helpful - I'm a noob with android :D)
You can do the same thing you did with Odin when you flashed the custom firmware. Just download your phone's firmware from http://samsung-updates.com/latest-firmware/ and flash everything in the downloaded files.