Can I just push the new project as an update of the old app that is already in the app store ?

I have an app at App Store from past two years, now I want to update that app with my recently created new version app for iOS11+ support.

My old app has different Xcode project and new app with different. in this case, xcode says to me keep a unique bundle id. So how can I update my old app with a new Xcode project, with the same bundle id...