Hidden navigation bar


I have a problem with the menu navigation bar on my site: https://goo.gl/uKFyzm
On the homepage it looks ok, but on the other pages and blog posts the menu is hidden or turns white (on white background, so it’s impossible to read it), which is something that didn’t happen up until a few days ago. Is there a way you can help me fix it? Thank you very much.

Hi Mrs Smith,
looks like you are not using our theme, please contact your provider theme instead