Class 'App\Http\Controllers\Backend\BackEndController' not found

[Maged Ahmed]

in admin when i try to reach any of (categories - skills - tags - pages - videos - messages )
i get this error
Class 'App\Http\Controllers\Backend\BackEndController' not found
as i can see the class already exists so whats the issue here ?!
p.s
i temporary fixed this by adding this line on each controller

use App\Http\Controllers\BackEnd\BackEndController;