And when you reinstall the WhatsApp application on one device, you will be able to restore these backed up conversations easily. The specific moving process could be:
Step 1. In case of losing data, you'd better backup the messages manually. Just open WhatsApp on the LG G4 and click on Menu> Settings> Chats> Chat backup> Back Up to backup the WhatsApp chat histories.
Step 2. Now just uninstall the WhatsApp from your LG G4 and download it on your OnePlus 6.
Step 3. To install WhatsApp on your OnePlus 6, you need to figure out what kind of SD card you have by checking the LG G4's specifications.
If you have inserted an external SD card to your old phone, you can take the card out of the device and then plug it into the new one.
If you only use the internal memory or internal SD card, you will need to move the "/sdcard/WhatsApp/" folder from the old phone to the same folder on your new phone. Just connect both your phones to computer and open the old device. Then find the "WhatsApp/Database" folder and copy the files that are created most recently. Next, paste the copied folder to the "WhatsApp/Databases" folder on your new phone.
Step 4. After the installation, you can launch the application on the Oneplus 6 and verify the same phone number that you have used to backup the chats.
Step 5. Next, just tap on Restore when you get a prompt asking whether to restore the found backup.
Then the chat histories that you have backed up on the LG G4 will be restored to the Oneplus 6.
— modified on Jul 3, 2018, 11:39:29 AM