Thanks, Piyush,

I do it as described, but the problem is, that the video-block gets always placed into the same container, but with "playing" around, I was now able to solve it!

1. Place the Text Block:
   • From the "Content" category in the right sidebar, find the "Text" block (or "Title", "Rich Text", depending on your needs).
   • Drag this Text Block into the left column of the "Columns" structure you just added.
   • Edit the text as desired.
2. Place the Video Block:
   • From the "Content" category, find the "Video" block.
   • Drag this Video Block into the right column of the "Columns" structure.
   • Click on the Video Block to configure it (e.g., paste your YouTube, Vimeo, or other video URL).
3. Adjust Column Widths (Optional):
   • If you want the text to take up more or less space than the video, hover your mouse over the divider between the two columns.
   • You should see a draggable handle or the cursor change. Click and drag this divider left or right to adjust the column widths (e.g., 60% for text, 40% for video).
   • Alternatively, click on the overall "Columns" block, and in the "Customize" tab on the right sidebar, you might find specific settings to adjust column ratios.
4. Refine Spacing and Alignment (Optional):
   • Click on either the Text Block or the Video Block.
   • In the "Customize" tab on the right sidebar, look for "Padding" and "Margin" settings to add space around your content.
   • You can also check for "Alignment" options within the block settings to horizontally or vertically align the content within its column.
     
     

Also consider checking: 
https://www.odoo.com/documentation/18.0/applications/websites/website/web_design/building_blocks.html