Problems in configuring CodeIgniter framework

Hi! So i’m really new to web building, heck even I’m new to CodeIgniter PHP framework.

I got a problem when bulding my web using webhost, I already uploaded all the my project files to public_html, set up and imported my database, changed my database configuration and base_url using the corresponding https://gnomepiex.000webhostapp.com/, placed my index.php in the public.html folder, but when I try to access my website, it show me this error:
Fatal error: Class ‘CI_Controller’ not found in /storage/ssd4/209/3733209/public_html/index.php on line 2

What should I do?

See your controller file names start with a captial?

yes it is start with a capital

my main controller is Andi.php and I copied it to the root folder (public_html) and rename it to Index.php