how to write any os of mobile phone symbain?

Do you have any idea how complex a modern OS is to write from scratch? Lets just try something: Write two methods to draw a line between any two points, in any colour supported by your display and then display a word of text below it in a different colour.

How long do you think it will take you to write that? In your preferred language, rather than one that is suitable for a mobile phone. If you think "less than a week" than you are probably a hopeless optimist! Now look at your mobile and see if you can spot how many of times those two methods are going to be called - just to display a small part of the stuff on screen. Then think: how do you read the touch screen? What protocol does the mobile phone use to talk to the base station? How do you read a graphics file? What processor is in the phone (Probably and ARM core design, but there are hundreds of them, all different)? etc., etc., etc.

Writing a modern OS is not a job for an amateur, it is a job for a large team. And none of them are beginners!
Find your self a more realistic target!