Update: The restore seemed to work fine. We got it working by using an UNC-Path plus setting the Security Restrictions on that share to "Everyone" temporarily.
What raises my interest here is: Setting it to Everyone is just not feeling right. What user should have had access to the share?
Next thing now: Recovery of Log Files. We wanted to restore the DB to 30.04.2015 14:00 h. So we created a corresponding template with this timestamp for point in time recovery. Restore worked great.
Question here: How can I make sure that the DB has the state from 14:00 h.
By checking the summary screen in DB studio I can see "Last Commit" was 12:05 h.
Regards
Daniel