display error about overlapping on mobile

Dear sir,

We met a problem which is the default theme and also other themes display on the mobile
As you see attachment, the list and the show board would overlapping.
Could you point us how to fix it and help to give us the code or offer the upgrade version to avoid the bug,
We are sure this problem is exist also on your demo site : https://www.joomunited.com/wordpress-demo/wp-file-download-default-theme/
https://www.joomunited.com/wordpress-demo/dropfiles-gdd-theme/
Please use a mobile like iphone , iphone6 , etc .

Thank you very much . We are worry about the issue for our customer. Will not accept the issue about mobile error display.

Best regard,

Alvis