To elaborate further: my earlier comment meant to suggest that the use of the '+' sign for 'expand' is a CORRECT way to do so. The problem was only in the MOBILE menu's arrows, which you have fixed now. Thanks.
( Also, for your use and info: in English, on Windows Computer systems, 'Context Menu' means the menu that pops up whenever you right-click on something. It's part of MS Windows and the browser, and no website can effect it. The sidebar nav menu in your theme is just called a 'sidebar menu'. Calling it a 'context menu' was a bit confusing when I read your site's tutorials.)
( Also, for your use and info: in English, on Windows Computer systems, 'Context Menu' means the menu that pops up whenever you right-click on something. It's part of MS Windows and the browser, and no website can effect it. The sidebar nav menu in your theme is just called a 'sidebar menu'. Calling it a 'context menu' was a bit confusing when I read your site's tutorials.)