It's a bit rough around the edges gameplay wise, but I love the world building you've done here ! The idea of the two world, with you making the connection between them is great. With the cool character design you've made, you have something solid to tell interesting stories ! Tighten up the physics a bit and it will be a great game ! A solid 5/5 for the use of the theme for me !
I think you could just use a simple rigidbody and change the gravity direction to make it more realistic, it seems you implemented a system that turns the ship in the direction it goes, which interferes with the physics.
Two other things that I think could improve the overall experience : in terms of pacing, the first levels are so quick that you barely have the time to understand what is happening. It is good to make it progressive, but there it is a bit disorienting. And the dialogue system could wait for the player to press an input to go to the next line, sometimes it went too fast and I had no time to read and understand everything (english is not my native language), and sometimes it felt too slow.