Excellent! I'm glad to see someone else using this tutorial!
Guillaume Tavernier's work is really beautiful and what you do with it is excellent!
If I may make one very small remark: I would avoid drawing the wall in transparency. I think you don't need it: we fully understand that there is a wall in front of us.
Did you try to just draw the door frames? Maybe that's enough (if doors are important).
That's only my opinion, but I find that the transparent wall spoils the beauty of your drawing a little.