How to read .CFG file in c#, and make in object so we can modify using that object.

It's your code as well as what is in that .CFG file holds so all this is up to you. You may have left out details such as you are using some system but didn't tell so as presented this one is "you and your choices." No one can tell you much as you presented the problem. Next time share enough detail and code and end your questions with question marks.