In general, not always, but usually, the error message is telling you what's wrong and what you need to do to resolve it. You had an incomplete restore, specifically on a file (which possibly suggests extra steps you haven't detailed here), you either need to complete that restore operation or restart it.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning