The problem with the ceiling is the perspective. Im sure that there are some great tutorials that could help you about this, its easier than it seems
with the perspective you have used in the picture, the ceiling would be impossible to see, it would cover part of the bg, and it looks strange. So, if you dont want to redo the background, you could try something like this:

its like if you would have taken the ceiling off, so you can see through it.
i´ve seen this style in several places, and it looks good to me.
And with practice you can get better and better in art, nobody is born knowing how to draw.
hope it helps
with the perspective you have used in the picture, the ceiling would be impossible to see, it would cover part of the bg, and it looks strange. So, if you dont want to redo the background, you could try something like this:

its like if you would have taken the ceiling off, so you can see through it.
i´ve seen this style in several places, and it looks good to me.
And with practice you can get better and better in art, nobody is born knowing how to draw.
hope it helps
