Each theme will have various building blocks that differ by theme. You can use the theme editor to customize how each block looks.
Navigate to Customization and click Customize > Home Page Customization. On the left you'll see the available blocks for your current theme. Read carefully over each section and as you make changes the page will automatically update on the right.
Most blocks will have a toggle to hide or show the block so feel free to disable any blocks you don't want to show on your homepage.
If you'd like to remove specific parts of a block or maybe add blocks from another theme you'll need some HTML/CSS/Liquid knowledge or you can hire a third party developer.