Blocks

Halyna,

It is unclear as to exactly what you would like to delete? Clarity is key in receiving accurate and helpful advice in forums such as this where the range of problems is never ending.

It is possible to delete everything you mentioned in your post including: specific instances of blocks, entire block module from the Moodle system, and entire courses.

to delete a block instance:
Find the instance of the block you wish to delete (on a course page, front page, etc). Ensure that editing is on (you must have teacher/course creator/admin privileges). Then simply click the small X icon that appears in the title/header portion of the block.

to remove the entire block module from Moodle system:
navigate to Admin -> Configuration -> Blocks from the Admin block. A list of the installed blocks is displayed. To remove a type of block, simply click the 'delete' link for that block. This will effectively remove all instances of the block and as well as the possibility of adding new ones. Only use this option if you never intend to use that type of block ever again.

to delete an entire course:
navigate to Admin -> Courses -> Manage Courses from the Admin block. A list of categories is displayed. Select the category the course is in to see a list of the courses. Find the course and click the X icon in the Edit column of the course list. This will delete that entire course.

Hope this helps,
dk