Fix erors in project

I have to submit a project as my B.Tech final year project. I downloaded a college management system developed in php. The system is working but 1-2 modules are showing internal error.
like when teacher or student login it shows error 500

Please fix all the errors

project file : https://drive.google.com/file/d/1DOtWPyeSf36AnPn0UV3AIp5HYhDB1QRr/view?usp=sharing