Tell me How do you keep saved?

I don't - God keeps me saved by His power, as the Bible clearly declares. Even when I am faithless, He is faithful.

What are your responsibilities as believer?

Lots - too numerous to name. Start from Genesis and go to Revelation - whatever wasn't fulfilled or done away with is our responsibility.

what is your difference from Heathen?

Now I am a child of God, joint heir with the Son of God, adopted by the Father, born again. I have also passed from death unto life, from the kingdom of Satan and darkness to the kingdom of God and light, no longer lost but found, no longer going to perish after this life but will dwell forever with God, eternal life not the second death.

what is the work of Holy Spirit in believers?

To regenerate those who believe. Tell me, how do you become unadopted, unborn, unsaved, unsealed by God?