Steve’s Barking; What dimension is the universe ?

I have a question for myself, what dimension is the Universe? We can see in 2 dimension and 3 dimension, or at least I can, but the Universe what I see isn’t what is real. What is up, what is down? What is sideways. There should be no left nor right. Everything we see is from the prospective of the earth. The earth isn’t flat even thought when most of us look into the horizon most of see it as flat (though some of us can see a slight curvature). This is true when I look into the night sky, the Universe the I see is flat and up and down, now I know this to not be real. So my question again to myself is what dimension is the Universe really and do we have to invent something totally new to navigate it?