All your photos are saved in a Google Drive folder. Follow these instructions to download your entire gallery in one action.
Click on the DOWNLOAD button in your gallery page.
When the new window has loaded and you can see the Google Drive folder loaded with all your images. Look for the gallery title towards the top of the page. The title will look like “Mr and Mrs Smith”
Click on that title to show the drop down menu,
Select DOWNLOAD towards the bottom of the drop down menu.
Google will automatically compress the entire gallery into one file and then automatically begin to download it to your device.
Once downloaded you will need to extract the file. How this is done depends on your device.