What I see from the screenshot shared is that you are trying to place a layout inside a layout and certainly that's no possible. You'll need to drag modules inside the layout and after that you can try adding more layouts.
If you are still experiencing issues with that it might be related to the theme you are using (had a similar situation once)
Let me know if you need further support and I'll be more than happy to assist!
What I see from the screenshot shared is that you are trying to place a layout inside a layout and certainly that's no possible. You'll need to drag modules inside the layout and after that you can try adding more layouts.
If you are still experiencing issues with that it might be related to the theme you are using (had a similar situation once)
Let me know if you need further support and I'll be more than happy to assist!