Main Menu Problem

Hi,

After the update, the main menu in the mobile version is visible as a white box (instead hamburger menu), and also it is visible in the desktop version while the horizontal menu appears.

I think it is with a custom CSS that have been made previously in the child theme because white box is not visible in the parent theme at live preview. But I’m having trouble finding and fixing it. Would be great to hear a solution.

Thank you.