Custom CSS not working

Things I’d like to do:
-remove the black border
-add a full-width photo slider on main menu
-remove the top menu. Adjust the widget menu color and transparency.
-etc…

But I seem unable to do anything on the website via custom CSS. I’ve searched the forums for similar problems, tried deactivating plugins, and refreshing, and updating posts, but still doesn’t do anything. Help anyone?

Website: http://mysticdervish.com/

Hi @jackchak,

I hope you are well today and thank you for your question.

Could you please share me the custom CSS code that you are using on your site to achieve this but it is not working so that i can help you?

Kind Regards,
Movin