Not responsive gallery in responsive content

Hi all,

I have migrated my website from html (built with dreamweaver) to wordpress. Now, I would like to adapt the pictures galleries to a responsive structure.
Here is an example of one gallery of my website: http://www.dday-overlord.com/mediatheque/photos-utah-beach/jour-j
The problem is that I have about 400 pages with pictures galleries and + 6,000 pictures with the corresponding legend. Do you have any clue to adapt these gallery with a code or to import the pictures automaticaly with the appropriate legend in galeries?

Thanks