Current menu item in secondary menu

Dear Enfold Support
I’m currently redesigning the website of a vacation home (see link to the website in private content) and run into the following issue.
In the header there are a main menu right to the logo and a secondary menu on the top. In the Enfold theme options I selected the page “Aktuelles” to display the blog page. To show my issue, the link to the page “Aktuelles” is placed in the secondary menu and in the main menu but in the end, only the secondary menu should link to “Aktuelles”.
If I go to the page “Aktuelles” by either clicking the link on the secondary menu or on the main menu, both links are marked as a current menu item (text color is black, see screenschot1). Within the HTML code, both have the CSS classes “.current-menu-item” and “.current_page_item” which I can style. As soon as I click on a blog post preview from the blog grid view and go to the single blog post view, only the link in the main menu stays as a current menu item. In the secondary menu, the CSS classes “.current-menu-item” and “.current_page_item” are no longer available and the text color stays white instead of becoming black (see screenshot2). But I want to have the link “Aktuelles” still marked as a current menu item because in the logic of the site architecture the single blog post is a subpage of the page “Aktuelles”.
It seems, that the secondary menu is not programmed in the same way as the main menu when it has to deal with a blog page. Do you have a solution for that issue?
Kind regards
Ueli