Hi,
Again this has been asked before and has not been fixed in recent template updates and has been discussed by many.
Your main menu is not showing subcategories at all in the desktop mode. Only showing in the mobile menus.
Completly useless and not been fixed yet.
There has been javascript custom code to add to the template and css custom to be added to the template, given in past forum posts older than over the last year ...But nothing works in the most recent versions of any or the past
Regards
Peter