Sorry for the late reply.
Kingroot and the other rooting apps used an old exploit which is now patched by Google in new phones.
I got my F3 Plus rooted and installed MagiskSU and XposedFramework by the help of this amazing guy.
Please contact Anh Duy on Facebook Messenger (or phdanhlc in xda-developers) and he will help you to get your phone rooted.
So save your questions for him because he will surely clarify them for you.