Hi Salah,
Before the step "Create Database", you must have installed Oracle DB Software as per the Installer directions. Can you please check and let me know the user/group permissions you set while installing the Software i.e. User Should be ora<sid> and group should be dba or something. Additionally sapsys group is also required.
You can check directly the user group ownership of /oracle/<SID>
Regards,
Akshay.