Menus are not change

I have a page from a customer and there you have to make the menu in more language.
I have the language German, English and Russian. Unfortunately if I change to another language the menu above will not be changed. I can’t find the error. Here is the page. https://benderbau.com/ If I choose english the menu does not change to english and stays in german. The same is true for Russian. This should be fixed, if I choose English, which also changes the menu to English.

The page I need help with: [log in to see the link]