>I removed about 95% of the size of the database by removing a lot of tables. The size should have been decreased to about 5 MB from 11 GB. However, after the operation, the database is still as big. I used the SHRINK DATABASE command but that didn`t change anything. I also restarted the service.

Use Shrinkfile command instead. Read comments to this blog:
Shrink log in all user databases