All I get when entering 0,26 euros is „Bad request 400“ 
@Andiweli
May I ask which page you are referring to? Is it a page on the app? It would be better if you could show some relevant screenshots.
Directly in the App settings. I am not able to enter „0,26“ it always prompts me the error as in the screenshot.
@Andiweli
After confirmation with the technical team, you can enter 0.26, but it cannot be recognized if you enter 0,26. The team will optimize this punctuation issue in the future. Thank you for your feedback.
Thanks! At the moment the onscreen keyboard on this screen doesn‘t offer „.“ - only „ , „ is available.