Where to change the menu item font size

my add to cart does the same - following this to see if theres a fix

You can edit it here:

/main/views/themes/tastyigniter-orange/css/stylesheet.css

1. in Theme setting, under Typography -> menu there is field to change the menu font size but it does not work. 2. partially display "add to cart"

see attachment for more detail

I have changed in the menu section (stylesheet.css) but the font size is not changed.