If you are switching services or want a full offline backup, use Google Takeout. This is the most efficient way to download thousands of photos at once. Go to takeout.google.com.
If you want to move your personal memories from the cloud to your physical device, follow these steps. Visit photos.google.com and log in. Click on the photo you want to download.
Google will prepare your files; this can take anywhere from minutes to days depending on your library size. You will receive an email when they are ready. 💡 Quick Tips for High-Quality Downloads
Click the three vertical dots (More options) in the top right corner. Select "Download" (or press Shift + D). Open the specific album in Google Photos. Click the three dots in the top right corner. Select "Download all."
Click on the image you want to download to open the preview pane. Right-click the image in the preview pane. Select "Save image as..." from the dropdown menu. Choose your folder and click "Save." Open the Google app or Chrome and search for an image. Tap the image you want to save. Long-press (press and hold) the image until a menu appears.