fix: fixed-navbar-at-top

[umangutkarsh]

ISSUE #420

fixes #420

The Ad-bar should be below the appbar. So, altered it.

This was the Issue^

Checklist

• [X] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [X] All new and existing tests passed.
• [X] The title of my pull request is a short description of the requested changes.

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