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I duplicated notes.php 

Like notes.php to category1-notes.php

And i I duplicated system_load.php to system_load1.php

And i edited notes.php and i I duplicated lib/classes notes.php to category1-notes.php

Now i can add and delete note in category1.php but i cant edit update. How can i fix that?

Please see how we are editing or updating notes

Another example for this please review Announcements module that also have edit and add features. 

We can just guide you we cannot provide you complete tutorial how you can achieve this.

But there are various items similar to notes, 

As we are adding User type and Annoucements status in Annoucements module similarly you can add, Categories in your notes to assign notes to different categories. 

To make a categories table for Notes check the user_level and make similar table and adding category feature so you can define categories.