Problem with dobble loading element

I have two elements that should be visible if I click one button.

In the workflow i did following: If >this button< is clicked >this element< should toggle and >this element> should toggle.

Now when I press the button everything is fine, but if i press it again, only one elemnt shows. Can someone explain why or how to make it function/better.

(The button is a button in the header which should show the navigation-menu for the mobile users)

If you didn´t understand my question, bc my english is very bad, just write me.
Else I thank you in advance for your time and help.