mobile

I am using lenovo S820. I updated my phone to kitkat 4.4.2 and lost root access. I tried various apps to root my phone and finally succeeded in rooting with vroot/iroot. As the app is in chinese I replaced the chinese super user with the supersu from playstore with the help of this link. http //forum xda-developers com/showthread php t=2532818. but now I am facing a problem that Firstly I lost root and secondly when I open the supersu apk I get a msg that "there is no su binary installed and supersu cannot install it. If u upgraded to 4.3 u need to manually reroot it. I tried to update the supersu apk from playstore but I get an error cannot update it. Please help how to install the su binary.