[politelemon]

This is the important bit. C4 in its entirety isn't useful to many orgs and teams, and can be unnecessary overkill. You might end up picking 1 or 2 layers for yourself.

You don't have to stick to their software either, use DrawIO if that's what you prefer, but understand the main concepts that C4 is trying to impart about the separation, what goes on the arrows, and how useless icons can be.