Your problems are challenging, hence why no one is brave enough to reply.I might give 100% wrong advice here, but give me a try.
I just stupidly removed my GBWhatsApp because I wanted to download a new version (the antiban 7.0.0), but it says no backup in SD cards, and I freaked out because I love to keep my messages, went through some Indian vids and found the answers, not like I know Indian language anyway
*This is from GBWhatsApp to official WhatsApp, but I believe the process is the same as it's all located in your phone data.
The trick here is you just have to transfer your GBWhatsApp database folder/files to your normal WhatsApp folder, but I will give the steps
Following the instructions
Download the normal WhatsApp, restore it like usual, and then back up it like normal in the chat backup.
At this point, you will only see the old chat that you last saved using the official WhatsApp before going to GBWhatsApp.
Go to your local files in your phone, find GBWhatsApp file > database, and find your last backup chat (if it's the only folder, that's the one, but if it has like 10 folders, the bottom one is your last backup. Mine is called
Copy/move (copy is preferable) that folder to WhatsApp > database
Go to Apps > WhatsApp > clear data, and then verify your number like usual. Then all your chats that your last backup in GBWhatsApp will be restored.
If you need vids help, search how to backup GBWhatsApp messages to normal messages working 100% by AB Tech on YouTube.
I believe you could do the same if you wanted to keep using GBWhatsApp. Just transfer your old GBWhatsApp database to the new one, and the problems would be solved. This is theoretical, as I have never done it.
I don't like using the GBWhatsApp anymore as it risks me losing all my backup data as it was not saved through Google Drive, it was saved only in your local files. So if you lose your phone and didn't back up all your files, you lose all the backups you made with GBWhatsApp. Sure it's no problem if you back up your files into PC by using HiSuite/Samsung Suite/Sony suite/whatever brand, but I prefer it being stored in Google Drive (cloud).
*Just wanna inform you that the GBWhatsApp backup is not saved into Google Drive, only into the internal files of your phone, so you can really screw yourself there.