Why is craftsman gas lawnmower have a 10 sec delay to stop when i let go of the handle that gives it power I have changed oil gas cleaned filter changed spark plug cord is op correctly?

Many small engines use a flywheel brake to stop the engine. (it also stops the blade faster than an electric cut off would)

Your problem is most likely being caused by the brake not being properly tensioned. Fixing this is NOT something a DIYer should undertake. Ask a local fix-it shop for help.