Version Change Problem

Hello everyone, im playing vanilla minecraft on java, and heres my problem. I had a server on 1.16.5 with a huge progress. Its been a long time after 1.17 update but this error did not change. I created a backup just in case the world crashed, but when i installed 1.17 for my server, everything changes. it didnt change to something cool but yet disturbing. Such as water splash turned into dragon flaps, tropical fish turned into a mule, glass blocks became leaves, and tridents turned into spawn eggs. So i thought i'll use the backup world, but its back to 1.16.5 i havent found an answer to this. is this an error or is it just impossible to transfer the world from 1.16.5 to 1.17