1) You need to set the frontpage as “Shop Page” (WooCommerce > Settings) or you can create a dynamic template (Abundance > Template Builder) which contains a product element. Apply this template to your frontpage.
2) You can create the mega menu via the menu manager (Appearance > Menus). Don’t forget to tick the checkbox “Use as mega menu” if you want to display the submenu items with a mega menu.
3) If you want to add a language switcher you need to use plugins like WPML. The theme includes a WPML config file.