Video from source file and cleaning up css files

Hi Gridbox team.
Have 2 questions:
1. I face the problem with video from source file.
It's always mute. Sound has to be switched on manualy when play.
Website: https://verrycherry.com.pl/pl/#home
2. How to clean up all custom settings done for desktop, laptop, tablets and mobiles, Is there any place where I could clean it just with one click to make everywhere same settings like on desktop?

Thank you
Michal

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