Your server timed out before the import demo content procedure has completed.
I suggest you setup a localhost on your computer as a demo site and import demo content in your localhost site. You can then use this site as a reference.
Please refer to this documentation for sliders. https://theme4press.com/docs/setting-up-the-sliders/
For menus, you can create a new menu in WordPress admin -> Appearance -> Menus
And assign it to Main Menu.
You can keep the demo menu as a reference.