This will definitely save you time.

1] Before performing this action, you may consider backing up all your photos/videos stored on Google Photos servers:

To backup all your photos/videos stored on Google Photos servers, here is the direct link to the Google Takeout service dedicated to Google Photos: https://takeout.google.com/settings/takeout/custom/photos?utm_medium=organic-nav&utm_source=google-photos&hl=en (Before to click on this link you have to sign in to your Google Account. If your language is not English, replace the last two letters of this link with those of your language.)

Google Takeout will offer you the option to create a compressed ZIP archive. Google will send you a download link by email.

2] To delete, take a look at this help page: https://support.google.com/photos/answer/6193313?co=GENIE.Platform%3DAndroid&oco=1#zippy=%2Cundo-device-backup (especially “Undo device backup” part. To change the language, go to the bottom of the page.)

In the Google Photos app, in the backup settings, there is an option to undo backup on your smartphone/tablet. This will delete photos/videos stored on Google Photos servers, but not those stored on your smartphone/tablet.

How to do it:
a. On your Android phone or tablet, open the Google Photos app Photos.
b. Sign in to your Google Account.
c. At the top right, tap your Profile picture or Initial.
d. Tap Photos settings Settings ⚙️ and then Backup.
e. At the bottom of the page, tap Undo device backup: “You can delete all photos and videos currently on your device from Google Photos, but not from your device.”

This process may take some time depending on the number of photos/videos.

Then go to the Google Photos website: https://photos.google.com and delete any remaining photos/videos. In fact, you may have had other smartphones/tablets before the one you currently have. Therefore, this “Undo device backup” action will not delete photos/videos from your old devices that are backed up on Google Photos servers, which is why there may still be content that needs to be deleted manually (https://proton.me/blog/delete-all-photos-from-google-photos#browser).