Richard I would attach screenshots but that is not possible via this avenue of contact.
Not sure about Android, but on iOS you can just long-press in the input text box, then add an image from that menu. (Or alternatively copy and image from somewhere and then paste it through the same procedure.) And in the desktop version of Together, you can drag-and-drop images.
Richard What must I do to contact support?
If you cannot use the app for some reason, send an e-mail to support@bunq.com with your request. This is also outlined on https://www.bunq.com/de/helpdesk