Help with CSS

Avg Bid (GBP)
Project Budget (GBP)
£20 - £250

Project Description:
I have a website and it uses the superhero theme

When I open the home page on a mobile browser I get a menu option, same as on the Demo (to try it change the width of the above page to around 200px).

However, when I open a post or a sub-page the menu is not presented correctly at the top of the page.

I would like someone to look at my site and tell me what is going wrong and causing this error, and to fix it for me.

Skills required:
CSS, HTML, PHP, Wordpress
About the employer:
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