What is the correct procedure to restore database in Drupal 7?
Deleting the database and re-importing an earlier backup is the correct procedure. Module states (enabled/disabled/version), content types, and other settings are stored in the database, so if those changes are not part of the backup you have, they will be lost. That said, you should be able to re-create them without any problems. 

Modules you've added since the backup will remain there as files, and you can re-enable them at will. There is no need to delete the files themselves.