The easiest way to recover App ,contacts,media files is to use Android data recovery program is to use Mobikin Doctor for Android,it is specially designed for Android and has powerful method to detect the data from trash bin.Then you can preview and choose the target files to recover.

To Restore App Data, Contacts, and Media Files from LG G6, before the data being overwritten, you can easily recover them with the help of Android data recovery software. If the data is overwritten, it's impossible to get them back.

NOTE: You can visit this thread for instructions on how to back up personal data.

Restore App Data:

1. Open “Settings”
2. In the “General” tab, tap “Backup & reset” under “Phone Management”
3. Under “LG Backup”, tap “Restore from backup”
4. Locate and select the desired backup
5. Tap “Start” to begin the restore. This may take a few minutes
6. Once completed, tap “Done”

NOTE: your smartphone might need to reboot to complete the process.

Restore Contacts:

1. Open “Settings”
2. Go to the “General” tab
3. Tap “Backup & reset” under “Phone Management”
4. Tap “Restore from backup” under “LG Backup”
5. Tap the “SD card backup” and press “Start”
6. Wait for the “Restored” pop-up and tap “Done”

NOTE: the process will require a phone reboot

Restore Media Files:

1. Open “Settings”
2. Tap the “General” tab if necessary
3. Under “Phone Management” tap “Backup & reset”
4. Tap “Restore from backup” under “LG Backup”
5. Locate and select the media file backup
6. Tap “Start” and wait for the “Restore completed” pop-up
7. Tap “Restart”

Restore Media Files from a Windows PC:

1. Connect the LG G6 to your computer via USB
2. Enable “Media sync” / “File Transfer” when prompted or from the “Notification” area
3. Launch the File Explorer on the computer
4. Navigate to and copy the media backup files on the PC storage
5. Transfer the files on the phone storage, preferably in the “Media” folder or the directory they originate from
6. Once the transfer is complete, eject the phone storage via system tray and safely disconnect the device from the USB port