To me, one "quick" improvement you could do is to change your introduction video. In the video, you spend a lot of time "browsing" a web without saying what you're doing or why is that relevant to the course. I'd try to do a shorter video with a voiceover where you state what is it that you're teaching in the course and what will students learn. I don't know if that would solve the problem but it's definitely going to help.
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