Menu on mobile phone - How to directly show second level of menu? Following configuration: Drupal 7, tb corpal theme, superfish menu

For mobile phones I get a menu as shown in the image. If I press the menu icon (1, red on image) I get first the "Main menu" level (2, red on image). After pressing "Main menu" the menu expands and one gets to the desired next level.



What do I have to change to get directly to the "second level" after "Main menu" level?
You can force the desired behavior via CSS or via Javascript (jQuery). For instance, check with jQuery if main menu is displayed on mobile. If so, then display its children, too. The CSS way would work if "main menu" is displayed by adding a class. If so, then you can, from CSS, display the second level when that class is present.