@Lakshmana ,
I think you should start your training from the beginning. You have alot of knowledge of different commands, file systems, scenarios, etc, but you always seem to struggle with the basics.
Linux or anything else in IT is alot like math in the way that you must understand counting, and addition and subtraction before you can learn algebra and calculus.
Check out udemy.com. They have some great training material at a very fair price.