Seeking advice for large-scale software project

I am a student in computer science currently attending a 4-year university. I want to be a software engineer. I am currently learning C++ and Python. One thing I'd like to do before I graduate is develop a successful software application that might be useful to the school I am attending.

My ideal software is an adaptive learning environment that could assist students while also providing data to instructors and administrators on student performance and what aspects of a topic students have most trouble with. I have the project drawn out, but it is a very large project with a lot of functionality. The software would be required to handle a LOT of data in order to perform analyses. It would also have to keep many database connections. One feature I want to include is the ability for instructors to see a students problem and assist them in "real time" by highlighting text and sending messages.

This is a long-term project that I intend on working with. I want to make the right choices technology-wise so that I don't end up developing a software application that doesn't handle well in the long run. I have two main questions.

1) My first question is whether I would benefit from developing it as a desktop application or a web application. I prefer desktop applications because I don't like bothering myself with browser stuff like CSS and JavaScript. However, it seems more and more technology are moving towards the web and utilizing cloud storage. I'm leaning towards a desktop application because from what I've read, desktops are more secure in addition to being functional even without internet.

2) This software would ultimately have many people connected to it at a single time. What performance issues would I need to worry about for a large-scale software application that will be handling large amounts of data, database connections, keeping connections between students and instructors, as well as serving educational material? What practices should I follow or technologies should I utilize to make the program run as smooth as possible?