Gmail account folders in apple mail keep disappearing

I use gmail accounts in the native apple mail app on iPadOS 16. I have various folders (not sub folders) setup in the native apple mail app to save many of these gmail emails into. However, not so long ago every single gmail was removed from those many folders. I have since set new folders up again just the same as before. I now find that again all my gmail emails have been removed. Can anyone please either tell me what I am doing wrong and how I can fix or stop this keep happening. Many of these are doctors/specialists and health emails which are extremely important and now I have no idea whatsoever when they were for. Am I best just to forget about apple mail and just use google gmail.

many thanks Liz