The layout does not show the way I would like it to show (like it shows on your demo). I use Mgs theme for reference.
Step 1: Add file: view/frontend/web/css/style.css
Step 2: Add file: view/frontend/layout/checkout_index_index.xml
Step 3: Delete folder: view/frontend/web/css/source
Note: With step 1 and 2, please find our instruction as attachments below.