Hi Ahmed,
Suggest you do the Build Your Own SAP Fiori App in the Cloud – 2016 Edition - Bob Caswell, Yoram Friedman, Oliver Graeff, Raz Korn, Ido She… free massive online open course. Although the course is now up to week 4 you can still join and access the videos and other material as a "self-paced" student. The intent of the course is to guide participants step by step through the design and development of Fiori apps including your own custom apps.
The course will give you all you need to develop your own Fiori app.
If you are in a hurry - you could also go to the previous version of the course Build Your Own SAP Fiori App in the Cloud - This will also give you enough to get started.... Just without the latest updates.
Rgds,
Jocelyn