In over your head
Neil deGrasse Tyson argues that if you’re given the option between taking a relatively ‘normal’ class versus an ‘advanced level’ one, you should almost always default to the latter.
I would have to agree.
Because grades, of course, matter very little after your second job. But what you learn from a course (or a job) can stay with you for life.
Better to default to challenging yourself above the norm (so that you can adapt concurrently) than to cap your learning, potential, and pay grade because you’re afraid you’ll do poorly.
If the experience (of being over your head) will pay for itself (in learning and exposure), you can probably get away with your performance suffering at least a little.