It worked!
Thanks so much! If I can spend you a coffee, just tell me 
Following config for docker-compose:
Note: You need to set the right access policies in the minio interface.
- PARSE_SERVER_FILES_ADAPTER={“module”:"@parse/s3-files-adapter",“options”:{“bucket”:“parsemedia”,“directAccess”:true,“baseUrlDirect”:true,“baseUrl”:“http://mydomain.de:9000/parsemedia",“s3overrides”:{“endpoint”:“http://mydomain.de:9000/parsemedia”,“accessKeyId”:“accessKey”,“secretAccessKey”:“key”,"s3BucketEndpoint”:true}}}