codeigniter data insert

I use a CMS which I bought from codecanyon which isdeveloped using Codeigniter, They frequently give updates and whatever custom work I have done will go off after the auto-update, I have to redo all the work again, Is there any way where we can insert data (Something like Opencart's OCMOD or VQMOD)? 

For example, there is a controller/dashboard.php file, if I have to insert any code or data to this particular controller or its function (to dashboard.php) without manually editing that file, is it possible? I tried using hooks but in hooks, I’m not able to insert the code to a particular controller or function.

Please help!

There's nothing built into CodeIgniter to do this. It would need to part of the code you purchased.
I suggest using git or some other version control to help with updates.
Start with a working version of the code and merge in the updates. A lot of IDEs (like phpStorm) can provide a side-by-side comparison of existing and new code to help resolve any conflicts.