I feel like if I ever get a professional programming job my biggest problem will be I can't work on projects with other people when it comes to programming I really don't know how to split up the work any tips?

It gets easier when projects get larger... Sure, it may be hard to split up the work early on, but usually you hit a point where you start seeing opportunities to parallelize development

Working with others is one of the most essential skills in the industry. Get some work experience in startups or small companies. That should teach you a lot. Key thing to remember is you'll not like everyone but you'll still have to work with them with a happy face.

Let's take an example, one class and two classes that are not that long, and each depends on each other. One does the large class, the other two smaller ones is done by your partner (you can switch yourself with your partner as well)

I don't think this is something for you to worry about right now. You'll almost certainly end up working with others that have this experience of breaking problems down. They will be able to guide you and the project so that you can start to learn the process for yourself.

@MightyNerd

Soon there will be a "Collab" tab/and or section in devRant where people can collaborate on projects. This can be kind of like practice for you.
You can read more about it here under "What's Next?"
https://www.devrant.io/news?n=5