I see a couple of issues. Did any of the content import when you imported the content?
1. Your site header is displaying. Slideout should have disabled this by default. You can disable it by creating a Layout Element, and disabling the header in the Disable Elements area: https://docs.generatepress.com/article/layout-element-overview/
2. You need to create a menu in “Appearance > Menus” for the primary menu location. This menu should only have 1 item with your site title in it. That site title menu item should have a custom class of:
Adding menu classes: https://docs.generatepress.com/article/using-the-wordpress-menu-builder/#custom-classes