If you like to discuss a new feature or submit suggestions, please use the community forum:
If you intend to send a bug report for Delta Chat, search for existing bugs first:
In short, the Android/iOS/Desktop parts are about the User Interface. The Core part is about handling the connection to the mail server and the chat or e-mail messages as well as providing secure communication by using Autocrypt.
A bug is a reproducable misbehaviour, when something happens but something else should happen instead.
Please try to create your issue in the respective issue tracker.
Did you know there is a Help page for Delta Chat?
To ask questions, you are also invited to join our IRC channel #deltachat.