Instead of inserting the Gallery directly on your page you have to use a Summary Block.
create a Gallery Page that is notlinked to the visible part of yoursite (and disable the page)
upload all images and descriptions into this gallery page (enterdescriptions in the little gear iconthat appears when you hover on yourimages)
In your public "film" page, remove the current gallery block hat youhave and instead insert a summaryblock. Choose a grid layout andspecify that the summary should bepulling content from the Gallery Pageyou just created.
Then choose what you need to display in your summary block: Title,Metadata...
More info on using summary blocks here: https://support.squarespace.com/hc/en-us/articles/206543337-Summary-Blocks