ImageOptim (download and install in local HDD) –> batch compression in Mac]
Now you can drag and drop all images in bulk amount here:
Step 2: Rename FILES (suggestion: add text before file names considering seo)
Now under ‘Photo Gallery’ plugin (https://web-dorado.com/products/wordpress-photo-gallery-plugin.html)
(1) first make a new folder of images (2) upload images (compressed) into that new folder. (3) add selected (CTRL+A) images into the gallery.
Step 3: Take URL of the new gallery like below and add it into Menu if needed.