I think this would be an option in your editor or template settings in Wix (there wouldn't be a Firefox setting for this). Maybe something in these Design settings for photo albums?

https://support.wix.com/en/article/wix-pro-gallery-settings-glossary#design-tab

It mentions: "Info Position: Choose to display the text above, below or directly on the gallery item."

Thank you so much for your response. I fixed part of them, but as you said, I will need their technician's help to erase the back-color of the text. Thanks again!