Retopology is just a plugin you can install it with 3dsmax 2020, 2021, and 2022. it is available on the Autodesk website and many other places.
I can also give it a shot but in my experience with this type of object, it will not be that good, because it works best when the object normal is perfectly in place and with bodyobjects it's not always the case. Check this one and see if this is what you want.
Almost half the size of the original file, of course, maps are optimized too.