Update- How to memorize textbooks or heavily information dense material.

I don’t know if I updated about this recently, but not too long ago I took the Japanese test.
All in all, I had to know 10,000 words, 2.4k kanji, and 1,000 grammar points.
I failed, but not for the reasons that you think.
The memory palace worked like a charm when it came to memorizing words, but I couldn’t get it to work for kanji.
After some time, I just forgot about actually studying Kanji, and the main problem was that I couldn’t read as well as I should have.
The problem is, the answers were written in Japanese, so I was only able to sniff out the answers from what I knew.
However, I did do very well in the listening section.
This took under a year and now knowing my mistake, I can continue and go back and do it quicker.

Speaking of which, I recently got into a Masters Program at NYU.
I have devoted myself to memorizing the subject material in the textbooks.
I have been having some problems actually thinking about how to take dense material and place it into a memory palace.
A lot of people mentioned different ways, but I have yet to see something that really clicks with me.
Any information you can give on subject would be amazing.
I am studying three months ahead of time, so if I can have all the information for the entire two years already pre-loaded, it would be amazing.

I do understand the amount of time and work it will take, and I am really looking forward to it.

So please, if you have any advice on how to do so, please let me know.

My first idea was to make a memory palace, not one that exists, and just have 2,000 doors.
But it seems the further I go, the more the information seems to blend together.
I assume this is due to lack of variation because all of the doors look alike.