Hi @laulau,
Can you tell us more about this course? I think you're saying it's a Canvas course site for a non-academic (not for credit to towards your school grades) purpose, is that correct?
If so, I'm not sure there will be a way to completely remove everything about that course from your Canvas dashboard without actually leaving it. I know a lot of schools/institutions/people like to use Canvas for unofficial things because everyone is on it so often and is familiar with it, but this is one of the downsides to doing that. Canvas is primarily designed as a learning management system, which means it's designed for academic course content. With that said, Canvas is also very flexible in options provided, but it's still at it's core a learning management system. At my institution, we don't allow anthing but for-credit courses to be on Canvas, partly because of issues like this.
I know this was more of a discussion than an answer, and as a student you may not have much control over these kinds of things at your school, but I hope the info helps! If I've completely misinterpreted the scenario, please let us know!
-Chris