Moving character....northwest...?

Because of my lack of english knowledge i don't know how to easily describe what i want better than to say: How do i move my character "Nortwest, Northeast, SouthWest and Southeast with Transform.Translate?

To make things clear my character is currently moving relative to the camera so i'm all good there, but i want to be able to move the character "Sideways-Forward" by pressing "W" and "A" at the same time. When i do it now my character either goes forward or sideways when i want it to go...well..."Northwest"...if that is the proper way to put it.

Here's my current movementscript...

         if (Input.GetKey(KeyCode.W))
         {
             Direction = Vector3.forward;
         }
         if (Input.GetKey(KeyCode.S))
         {
             Direction = Vector3.back;
         }
         if (Input.GetKey(KeyCode.A))
         {
             Direction = Vector3.left;    
         }
         if (Input.GetKey(KeyCode.D))
         {
             Direction = Vector3.right;    
         }
         Direction.Normalize();
         transform.Translate(Direction * MovementSpeed * Time.deltaTime);

Sorry if i'm being unclear. Thanks for reading!