Updating your personal snap package

I am creating a project using the dump plugin, how to make it so that when updating the project, it updates the project, and does not upload a new one

Each new release of your application is a different squashfs mounted on /snap/<name>/<number>. Files that survive updates should be written in a separate data area, typically pointed by the SNAP_USER_COMMON environment variable. You can check the environment variable reference for more information about this and other environment variables that may be useful when creating a snap.

Did I understand you correctly
I have to in my snapcraft.yaml specify which files will be writable