so i figured out how to do this.
you can use the parser linked above to check if your edits are right.
values in hex are stored as little endian float, use this website to convert
https://gregstoll.com/~gregstoll/floattohex/ (make sure to check swap endianness since big endian is default!)
now you can kinda go by trial and error with the help of the merged json file. simply look at the json, pick the number you're looking for (movespeed for example) convert it with the website and then do a search in hex for it. then just change it to whatever you want. values that can only have whole numbers are just stored as a normal hex value.
in the game im making a mod for, the default offset between values seems to be 0x1D but that could be entirely different for you.