@ldez Thank you for your effort! I dont know why but this does not seam to work in my case. I am also wondering why there is a difference between the app service and the api. The app is Nginx and the api is a node container. Here is my repo:
https://gitlab.thiloilg.com/repo/blicc/blob/master/docker-compose.yml
The weird thing is when I expose port 80 separately for each service it works perfectly.