The fourth physical dimension

We know One dimension, two dimension and three dimension. Lets try to imagine a fourth physical dimension. To do this imagine a world with only two dimensions called ‘2Dville’. In 2dville, people exists as different 2d shapes. Each of them have length and breadth but no height. They know only length and breadth and they don’t have any idea of what height is. They cant see up because they don’t know ‘UP’. Now suppose a creature with three dimensions, say ‘me’ , sees this 2d world from above but the people of 2dville have no idea that they are being watched. If I speak, the people of 2dville can hear me but it would be like a voice from nowhere. Also when we try to pass through 2dville, the people of 2dville see flat images of changing shapes and once you pass through completely you seem to dissappear.

So according to the 2dville guy, a shape appeared from no where and its shape changed and finally it disappeared. Shocking . Now imagine our world and that we 3d people are not aware of the 4th dimension. We cant see it but what if things existed in the 4th dimension? They could see us and we cant see them. Even if they passed through our dimension we still see a three dimensional figure momentarily. What if when people die they go to some other dimension? And sometimes when they pass through our dimension... Are they spirits? Ghosts?