Hero not showing on mobile

In https://wordpress.org/support/topic/hero-not-showing-on-mobile/#post-13344238 I asked why the hero-image on https://mondzorglia.nl is not showing on mobile. Kharis Sulistiyono provided some css to fix the problem and it works just fine.
Still I would like to know where the css that caused the problem comes from since it’s not part of my css as far I know.

Best regards Bernhard

Hi Bernhard,

Thank you for reaching out to use.

I have just sent you a direct message and you should have a waiting-response message in there.

Regards,
Kharis
aThemes Support