Changes lost after updating Nextcloud

Hi there!
We have modifed .scss files while we were on v23.0.2 and then we upgraded it to v23.0.3 and the changes are lost - which makes sense cuz we have to modify them again.
We are just wondering if we could find a way to make our changes last even after later updates and releases.
Any idea?

You know where the scss-files were located?
If you used the updater app, there is a chance that it might be within the backups → datafolder/updater-randomstring/backup/…