I could resolve these problems, maybe the documentation can be updated?
1) i use the latest docker-version on windows
2) use the docker-compose - Version 1.25.5 (in the docu is version 1.24.0 linked)
3) i am currently using OCAML 4.08.1
4) i have cloned the latest unison-code from github and compiled it
after that, everything works like a charm