got some weird result with screen edges after shading the controller 
Hi Ahmed,
That might be because you don't have Auto Smooth enabled...which you can't, because that has been removed in 4.1...(don't say we didn't warn you to use the Version used in the Course 😉)..
So, you can go to Object > Shade Smooth and then Add a Modifier > Normals > Smooth By Angle..
It could also be, in addition to that, that your Faces aren't completely 'flat', but try the Smooth By Angle first and maybe play with the Angle if necessary.
But something else, why did you disable the Noise Threshold?
Rendering on CPU with 4096 Samples will take 'forever'.
Rendering and what Settings to use is a huge topic, but as long as you don't know what you are doing, it is best to not change the default Settings.
I tried to shade smooth then add a modifier .. but it doesn't work
I didn't disable the Noise Threshold on purpose I it was just by mistake
and I changed from CPU to GPU and it is faster in rendering thank you for the note
If the Smooth By Angle Modifier didn't help, then there is probably something wrong with your Mesh. Hard to diagnose from the screenshot alone.
If you want you can upload you .blend file to Dropbox, Googledrive, or so and post a link here, then I or someone else can have a look at what exactly is causing the issue.
