From the picture it looks like you're using the CMSJunkie template. If so, go to your joomla themes menu and click on the theme you are using in that image menu. There, click on the option to change the theme settings. It will open a new page with several settings, I found some related to how the menu appears on the site. If I'm not mistaken there will be two options.
I looked on your website and the letters do not appear because they have the same background color as the google map module. As I said in the previous paragraph, in this configuration of the theme you can also change the colors.