How do i put a responsive block behind a youtube video?

Hello!

I’m kind of new to webflow so i’m not an expert.

I want to put a white block behind a youtube video like this:

Here i have put a white div block behind the video by using the spacing sliders.

When i publish the site however its all messed up. The sizes change and so do the locations.

Example:

What am i doing wrong here? how can i make this work?

Thanks!