Traveling the Universe

The universe is boundless. Without oxygen, how can humans travel in the universe? The nearest galaxy to the earth is 340 million light-years away. Even if a spaceship travels at the speed of light, there is not enough life to go there. So are humans really trapped and dead in the solar system? It would be a shame if that was the case. It just so happens that humans still have imagination, and those fantasy novels have given us inspiration. Can we use the skills of fantasy novels to travel the universe? I thought this method was very interesting, so I tried to write it. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.