Enter query to see what connections to database were open:
Enter this query to manually kill if needed
Then was able to take DB offline.
Take SQL Server Agent (OptivaDev) for that particular DB offline.
Restarted SQL Database (OptivaDev) service because restore was failing with unexplainable generic errors.
Restored DB, and restarted SQL Server Agent (OptivaDev)
When doing tasks -> restore -> database, find the file you want to restore from. and specify the DB you're restoring to. THEN in the options tab, you need to checkbox "overwrite the existing database (with replace)