Hi Muhammad. When you perform a course backup, there is a page where you can pick and choose which course activities and data you want to include in the backup. I don't think that there is an option though, to not backup the the course files related to the course. Perhaps there is but I don't know about it, and I need to defer that to someone who knows better.
I have had use cases where it would make sense to have an option to backup an entire course, including all completion data, gradebook, essentially all the db stuff, but to exclude the related course/activity files (the files that are stored in the Moodle data directory). If it is currently possible then I am not aware of it.
Sorry I'm not of more help on this.
Jamie