The app needs a lot of improvement. I’m trying to pay my first “Rechnung „ and the app doesn’t work. It doesn’t let you go ahead. I don’t know now what are the credentials for the payment . The full information should be given also in an email to allow the client to pay per SEPA. It looks like they are forcing to pay per direct debit. It should also be possible to choose the language of use giving English as an option(even for foreigners living in Germany).