Why are we not crushed by the weight of the atmosphere

(I'm not completely sure what your current curriculum wants you to answer with, but I'll provide one way to answer the question)

Yeah, the weight of the atmosphere is heavy. Extremely heavy, actually. However, we humans are not crushed under its weight because of what is inside of us. While there is a lot of external pressure coming onto us from the weight of the atmosphere, the internal pressure of what we are made of balances it out. This is because humans are made up largely of incompressible solids and liquids.
If you want an example of this, you could imagine a balloon filled with water. Attempting to crush the balloon would serve as the external pressure, while the internal pressure would be the incompressibility of water. If the balloon were to break, it would not be because the water was compressed. It would be because the water was unable to be compressed, and ended up forcing its way out.