Hi Axel,
You can refer to the Fiori app reference library Fiori Apps Library and check which of the above apps are available as out-of-the-box standard apps. Those of which are not available as standard can always be developed as custom Fiori apps.
If some of the apps are using approval workflows in the backend the you can use the My Inbox Fiori app to enable approve/reject for these (Approve Requests is the predecessor for My Inbox, it is recommended to use the newer My Inbox app).
Regards,
Saurabh