If you'd like to better understand student reviews, you'll have to ask them. Ideally, in a conversation with a few of them, rather than a survey that doesn't let you ask clarifying questions.
As a Master student in CS myself, I'll go over your bullet points to give you my thoughts, but keep in mind that I have not experienced your course.
For the university level (master degree), I believe I have to explain on a higher level and not like 3brown1blue videos.
There are some very high-quality videos on youtube. They don't go in-depth as much as the university course should, but they are amazing for understanding the rough idea. In my experience, a lot of lecturers don't give an introduction and overview, they jump straight to the rigorous math and leave me wondering what exactly we are doing, why we are doing it, and whether this is something I should be able to follow or even come up with myself.
Personally, I prefer learning with just youtube and blog posts, plus the university course's exercises + solutions over a live lecture that I can not pause, vastly. All I need for that is clear keywords on the slides so I know what I need to google and how much I need to grasp of it.
clear and informative slides,
which you are covering well. However, other students who prefer a live lecture will gain less from the "informative slides" and would prefer them to be light on unneccessary details. "A good talk has very little text on the slides" vs "Good lecture slides make the actual lecture redundant".
Now one solution is of course to have a lecture and a different script for self-studying. Which is generally nice, except
explanation on a digital board + the slides (the only course providing recorded slides and board)
Make sure that it is clear which parts need to be looked at as necessary and sufficient for the exam. One course I had this semester provided additional video recordings as replies to some student questions, had lecture slides, video recordings where the lecturer stated more than was written on the slides, exercises that seemed to deviate from the lecture, graded projects that were fully off-topic in my opinion and distracted from actually learning anything, and reference material book chapters.
The book chapters were all very good! But reading the reference material from just a single day's lectures would already take me two weeks. And when I asked what was relevant for understanding, and what for the exam, the answer was that all material might contain something the other stuff does not was very unsatisfactory.
So please make sure you aren't overwhelming your students by giving them a lot of "helpful material" that they then have to work through in addition. (Or think that they have to).
we even covered the fundamentals of linear algebra and math in general as a bonus because I noticed that my former students had a problem understanding some topics because of this.
This is great for the struggling students, and boring for the ones that already got it. Perhaps some students are giving you worse reviews because of this. If you can start this kind of lecture with a slide that summarizes what will be covered to allow students to see if they need this lecture or not (and tell them this is the intent), that could help.
"Do I really have to look at those? I already got the main concept but maybe the exam will ask about this specific example..."
One thing you have not mentioned yet is how clearly you state the goals. I find clear goals very useful, such as:
- What is relevant for the exam
(Exams are often just barely related to the actually interesting topics. Because the interesting part is harder to actually test.)
- What is just additional info for those interested
- What is not even really meant to be understood? (e.g. some proofs on the slides)
- What are students supposed to learn in
- This course
- This lecture session / This exercise
the best possible video and audio quality,
exciting and interesting weekly tasks,
we also made the course hybrid: online, on-campus and recorded (the only course provided with this format at our university).
I love that! With all the thought you are putting in, you probably got this right. But for completeness: Hybrid can be a terrible experience compared to online-only. Things I've experienced that are negative examples:
- Lecturer used laptop microphone for zoom, and worn microphone in the room. So everyone who was there in person understood perfectly fine, but whenever the lecturer walked one step to the side, we wouldn't hear anything online.
- Chat was not monitored.
I find one of the biggest advantages of online lectures how easy it is to interact with the lecturer. I can simply unmute myself and ask when something is unclear. Compare that to raising your hand for ten minutes, then yelling "sorry?!" and still not being noticed, in the lecture hall. But even with this pro gone, just having a chat that the prof notices works well. Having a TA monitor the chat instead is alright too, but then no interaction is possible anymore.
- Lecture took place in-person only, exercise session directly afterwards took place online-only.
I master the topic very well now,
That's great, but does this make the course harder as well? It sounds like you did a lot of additions that would be very useful for learning the topics of your course. But sadly, your course is probably less than a third of the total credits students are supposed to take in one semester. Where every lecture already is more effort than it is supposed to be. If I feel like I have to put in nights and weekends to fare somewhat okay in your course, that will negatively influence my review of your course.
Also, is your presentation still aware of the difficulties that people have with the topic when they first encounter it? Perhaps you've mastered your topic too well and assume things are obvious that you yourself also didn't grasp instantly.
we had to search by ourselves to understand
Keep in mind that this can mean multiple things. Maybe you did explain it in a way the did not understand, yes. Or maybe you explained things that were too obvious so it was confusing because it was not clear why you were even explaining in the first place. Or maybe it just took a while to really grasp it and reading it up online worked, but watching the lecture a second time a week later would also have worked... This is looping back to my initial advice: Perhaps you can ask some of the students how it's going.
For example, you could casually do some small-talk with students in the break when there are no more questions. One time a lecturer did this and realized thanks to that that we actually had none of the ~five prerequisite courses he assumed everyone must have taken before his lecture ... he didn't realize that CS students didn't even have the option to take those prerequisite lectures and still his course was one of the recommended three to us.
He also started to summarize in between subtopics "What did we do. Why did we do it. What do we want to do next. How will we do it." after our casual feedback, and that made it a lot easier to follow.