File-Backup on Synology NAS: How to restore single Files? (*.enc, *.gze)

I’m new to UrBackup and don’t understand *how to restore / decode backup files *.enc, .gze
(I read the manual and the wiki, but this proceder might be to basic too be descirbed?)

Please give me a hint how to handle these files.

Background info: UrBackup Server 1.4.10 runs on a Synology NAS DS215j.

All clients to be backuped use Windows 7 or 10.
File backup is configured to the shared folder /volume1/Backup_Clients/client-name
This folder can be accessed from the windows client and holds the mentioned ENC and GZE Files.

log file looks good, despite these 3 errors:

backupcom->AddToSnapshotSet(volume_path, GUID_NULL, &dir->ref->ssetid) failed: EC=VSS_E_OBJECT_NOT_FOUND
Creating shadowcopy of “Client” failed in indexDirs().
Activating shadow copy on “Client” for path “Client” failed

May I kindly ask somebody from the comunity to help me out and provide a short answer - even if this may be a beginner question?
Thank you.