Here are the steps required for rerooting the device. So first we are going to unroot and remove kinguser app. And then we are going to use supersu for rooting the device.
Steps for removing Kinguser root settings.
1. Open the Kinguser app.
2. Tap on gear icon to go to settings.
3. Tap on root authorization settings.
4. Tap on remove root permission option.
5. Tap on clear option that says "remove root permission resets and returns unroot status".
After the completion on this process you can uninstall the app. Also do clean any settings files that remained orphan after un-installation of the app.
Before you reroot the device, I suggest taking the device backup. You can use any cloud app for cloning the settings. Also you can take system recovery through various open source tools out there. You can use TWRP for this task.
Rooting using the supersu
1. Download the latest version of supersu through this link : https://download.chainfire.eu/supersu
2. Store the zip file into internal storage of the device.
3. Boot into recovery mode using TWRP or any other recovery mode software.
4. Open the supersu through recovery mode.
5. Flash the device using Wipe cache/Dalvik" button. After that click on Install button and locate the supersu.zip.
6. Let the process finish properly do not press any other button or tap on screen.
After the process finished, you can reboot into the device and it'll show the supersu app in the app drawer. This should let you root and unroot using the supersu app.