Hello,
01. This demo utilizes a blog widget on the homepage. To achieve the same layout, add the blog widget and navigate to the Style tab. Select Blog Design: Carousel and Carousel Design: Default to match the demo’s appearance.
See Screenshots for better understanding:
https://ibb.co/x0srxHx
https://ibb.co/dJcM7ZTT
02. This is called Sticky Navigation, you can Navigate to Theme Settings > General > Sticky Navigation > choose/modify the menu. You can read more about it here: https://xtemos.com/docs-topic/sticky-navigation/
03. Navigate to Theme Settings > Styles and Colors> Buttons > In the Advanced button styles section, you can select the Add to Cart button in the dropdown and change the background color: https://ibb.co/zTRdCkcs
Please Follow this guide: https://xtemos.com/docs-topic/advanced-button-styles/
Best Regards,