I haven’t learned any general relativity yet, but from what I know of special relativity, it actually makes perfect sense. You start with the assumption that no observation can allow you to deduce where you are or how fast you are moving, and then follow that premise to its logical extremes.
You also need to know that there’s something that travels at a finite speed in vacuum, otherwise Galilean relativity is consistent with that assumption too.
You also need to know that there’s something that travels at a finite speed in vacuum, otherwise Galilean relativity is consistent with that assumption too.