I uploaded everything to my webserver, created a mariaDB database + installed Java (because my debian did not have it yet) but the setup does not work for me.

Are the commands in the Readme up to date?

I tried these

# Create database tables
bin/server -DdropAndCreateNewDb

# Create admin user
bin/server -DcreateAdminUser

# Run application
bin/server

But already the first throws a lot of errors. I am not quite sure what to look for.

E.g.: One error marked red says "[error] application - Error when parsing accounting-config.yml: java.nio.charset.MalformedInputException: Input length = 1"

Really looking forward to you reply as I'm really interested in trying this tool :)