You cannot resolve that simply because Gantry 5 is not yet Joomla 4 compatible.
You can find the answer of all your questions in this discussion and the links in it.
Subscribe to our mailing list and stay up-to-date with all our awesome releases, latest updates and amazing discount offers!
The Joomla!® name is used under a limited license from Open Source Matters in the United States and other countries. InspireTheme is not affiliated with or endorsed by Open Source Matters or the Joomla! Project.