[Gelöst] Double menu items in English mobile menu

Background of the issue:
I am trying to resolve an issue with double items in the English mobile menu on my site versteckter Link. The Dutch menu is standard, and both the main menu in Dutch and English are good. The mobile menu in Dutch is also good. However, I cannot edit the English menu due to synchronization settings.

Symptoms:
I see double menu items in the English mobile menu.

Questions:
How can I remove the double menu items in the English mobile menu?
What steps should I take to resolve the synchronization issue preventing me from editing the English menu?