This is a good first attempt. I'd suggest before you go further though to read my Beginner's Guide clickable from my signature.
You don't show your walls, so I don't know if you have a reach problem. Figure about the most you can go is 30".
Now for the layout itself. First of all, this layout does not appear to have any purpose. A well-designed layout will represent a section of a railroad and even if a loop is closed, still goes from point A to point B. The purpose of a real railroad is to make money typically by moving goods and passengers. A model railroad will do the same, even if all we do is watch it go through scenery.
That said, your design is a little lopsided. Your roundhouse grossly overpowers your yard and your yard over-powers the rest of your layout. Other than park your trains and run laps, there's very little to do.
Even if your layout was the size of a warehouse, without things to do, you will get tired of watching your train run laps. You need to add some kind of operations either freight or passengers or you will outgrow your layout long before you finish it. I suggest reading
Track Planning for Realistic Operation by John Armstrong.
Because your levels are so close in height, changing elevation does not gain you much. You might have just as well run one level. On the other hand, if your track ran down a level to hidden staging, that would significantly increase your operational ability by virtually extending your layout.
See my article:
What is Staging and Why do I need it?
Finally, a small point in all this, but having to reach over a trestle on the edge of a layout to something lower is a pain in the butt. I made that mistake on my first layout.