SUCCESS!
Finally. Sorry Parth, for the confusion, I should have tried harder before posting.
In "Options" I checked "Overwrite existing database" and it did the restore. I had some more trouble, because I didn't fully understand step 9. But made it finally. In table "dbo.ServiceData" I had to replace the Service URL for 8 different records. (HASPClient, HASPAdmin, HASPDefine... )
I restarted the servcie, and finally the data is here.
Thanks a lot!
Now I need to understand, how to migrate with this outdated Business Studio 5.12, to a state of the art solution. I'd appreciate some guidance.
Thanks!