I cannot select a 3D object from scene with the mouse I only can select it from Hierarchi area. Please I need help.
Are you sure you are in the scene view and not in the game view? What version of Unity are your using?
I have had a weird bug crop up from time to time that sounds like that. My solution has always been to reset the layout to default settings (Window -> Layouts -> Revert Factory Settings). You'll have to lay out the windows again the way you want them once it's done but it has solved the problem for me everytime it happens.