Feedback on course

3 things I would suggest.

You have great looking navigation buttons. It's just a personal thing for me, but I don't want my work to look like it came out of a can or cookie cutter, or ready-made off a shelf. So I use custom navigation rather than the built-in Next and Previous. Yours look good and add a touch of class. I would get rid of the built-in ones.

I would definitely organize the menu (which I never use) to be in the same order as the slide progression. I much prefer a slide that gives learners as many options as possible, and never use the words Next and Previous. They are too much like reading a book.

You should create a drop target where the dropped items won't cover up the words.

I've implemented the principles of some of these suggestions in the attached sample. You'll find plenty of places where I didn't complete the details, should any of these ideas strike your fancy.