In order to flush toilet I have to hold handle for excess time

SOURCE: Holding down the toilet handle till flushing complete.

No you just need a new flapper for your flush valve. Its just a 2 minute job.

SOURCE: Great unit!

Thanks

SOURCE: toilet flushing sytem

your chain on your flapper is to long,adjust to proper hight.

SOURCE: Kohler Toilet year old do not have flapper. It has stright pipe

This is how it is meant to work!
Short push of lever for small flush, push and hold lever for full flush.

SOURCE: When I flush the toilet the handle stays down and

If you lift the lid you should see where the handle goes through the porcelin. You can remove the handle by unscrewing the nut inside the tank. Try cleaning the inside of the nut as sometimes water deposits collect in this area and cause binding on the handle shaft. After you clean it up you can apply a very small amount of petrolium jelly to the handle shaft when you reinstall it, this should prevent the problem from happening again.