Q: whenever i want to download updates from App store apple id password is flashed of my previous shared user instead of mine At present i am the only user

What do you mean by "previous shared user"?  Did you previously use a different AppleID shared with someone else?

All purchases from the App Store are invariably tied to the AppleID you used to download them.  That cannot be changed.If you want to update an app or the system installed or purchased with a different AppleID, sign into the AppStore with that AppleID to install that update.