11 hours for restoration of 100 GB database doesn't sound reasonable. Can you please let us know your backup strategy? How are your full backups and delta backups scheduled?
What are the parallel backint backup channels used during backup? Restores typically use the same number of channels used during backup.
But unfortunately HANA considers parallel backint channels if the backup size is over 128 GB. We need to see if there are any recent changes on that.
You can also consider using IntelliSnap for faster recovery options.