After clean installation of macOS Catalina: storage space optimization does not work correctly

When starting storage space optimization I get the following message:

"La cartella di sistema e quella Inizio non si trovano nello stesso volume.

Con la configurazione attuale, alcune funzionalità di ottimizzazione dell’archiviazione non saranno disponibili."

In English this should be something like: "The System and Start folders are not located on the same volume. With the current configuration, some storage optimization features will not be available."

I need to add, that while installing I had issues with the installation and I needed to erase and recreate the partitions "Macintosh HD" and "Macintosh HD - Data". Without that it would not have been possible to continue with the installation. After the installation finished correctly, the user folder remained on "Macintosh HD", so I moved it to "Macintosh HD - Data" (via "system preferences" => "users and groups" => right click on user => "advanced options").

Somehow the system works but I have the impression that it did not install 100% correctly. In fact, in disk utility I can see now two "Macintosh HD - Data" but I cannot delete the one which I do not need.

I hope someone can help me out with this question. Thank you so much!