Ruby on Rails 6 + Active Admin, add basic functionality

Ruby on Rails 6 + Active Admin, add basic functionality

I want to add some functionality to an existing rails app, a school's admin website.
Relevant gems:
rails 6.1.6, activeadmin, activeadmin_addons, arctic_admin, activeadmin_quill_editor, cancancan.

1 - Add files attachment functionality to announcements, messages and events:
Currently all 3 have a title + description + recipient, we want to add the hability to attach multiple files to the content
Message reply is currently done with a "custom view" instead of the normal "Active Admin" way, probably better to switch to the active admin way.
This is the main task

2 - Add a single view for the events details:
Currently created with title, description, recipients, date, schedule, but the view is only at a calendar level (titles in a calendar)
User should be able to click on the event and show a single view with the event details

3 - Improve dashboard:
Currently shows the contents of announcements.
Add 2 sections with a list of unread messages and upcomming events.
If no announcements/messages/events are available, show a welcome message.