Please how do i flash in or update my Oukitel u11 plus OS/firmware to the original or updated one

Someone mistakenly flashed in an outdated firmware into my new oukitel u11 plus..now I just hate the phone because it doesn't show to be Powered by android on start up anymore, neither is it even certified by Google play too anymore,etc

Start here. Then click the "Guide to Flash Stock ..." button on the bottom to get to here for instructions.