Download all photos from google photos at once
Google Provides service named takeout from where you can download each and everything. Using takeout you can download photos, videos, emails, contacts, blogger, chrome, etc. Link :- TAKEOUT BY GOOGLE
The downloaded file will be in compressed format (zip or tgz). For tgz you need to install additional software on Windows.
Try to Download files in 1GB or 2GB size, so they can easily be accessed. After completing all the steps you will get the mail from google on your registered email id within hours or days that your compressed file is ready for download.