I’m having difficulty accessing the gallery if I need to go back and edit it after finalizing it. Can you give me a hint what I need to do that I’m not doing?
Could you please let me know which gallery are you exactly referring to on your site? If you are creating and modifying default galleries, which you can add to Pages and Posts, then please have a look at our support article with a video guide on the below link: https://en.support.wordpress.com/gallery/
If the article does not answer your question, then could you please link the gallery and I will take a look and guide you through how to modify it. Thank you!