If you are using Google Photos app then follow below instructions to enable automatic back up & sync to keep safe your photos forever….
1. First install Google Photo app from Google play store on your smart phone.
2. Open Google photos app in your mobile phone.
3. Now see at the top left and tap menu
4. Select settings > Back Up & Sync
5. At the top, switch it on or off
6. Select backup account
7. You can also select backup device folders like…
You can also keep backup of photos manually on desktop PC.
Few things you need to keep in mind about setting option.
1. If you changes backup settings then it will affect all apps that uses Back up & Sync, such as Google Drive.
2. If back up & sync setting is on then uninstalling Google Photos app from your device will not turn it off. If you want to turn off back up & sync then you need to follows above instructions.