Grid (collapsed) causes a large white apace below footer

Good morning, I am building up a website on a local server (therefore, no link, sorry).
I am a beginner in web design and Bricks, specifically, but I think I learned a lot in the last weeks.

But I cannot get one problem solved:
I created a grid with one row and three columns for desktop view, which works fine. Now, for mobile view I want to replace this grid by something else for better user experience, so I collapse the whole section which contains the grid. This does work, yet it leads to a large white space underneath (!) the footer. It must be due to this hidden element, because when I delete it, the issue is resolved. I tried and tried, but cannot figure put what to do. Any suggestions what the mistake is? Thanks.
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Meanwhile I understood that this is an overflow issue. Can anyone help get rid of that?