See the article https://support.apple.com/en-in/HT204264
- On your Mac, go to System Preferences > Apple ID. Click iCloud in the sidebar, then select Photos. If you have an earlier version of macOS, go to System Preferences > iCloud. Click Options next to Photos, then select iCloud Photos.
Pause library uploads to iCloud
When you turn on iCloud Photos, the time it takes for your photos and videos to upload to iCloud depends on the size of your collection and your Internet speed. If you have a large collection of photos and videos, your upload might take more time than usual. You can see the status and pause the upload for one day.
- On your iPhone, iPad, or iPod touch, go to Settings > [your name] > iCloud > Photos. You can also open the Photos app, go to the Photos tab, and scroll to the bottom of your screen.
- On your Mac, open the Photos app. Select Photos in the sidebar, then click All Photos in the list of tabs in the toolbar. Scroll to the bottom of your photos and click Pause.
Read the preferences article for photos https://support.apple.com/en-in/guide/photos/pht5156cc968/4.0/mac/10.14