He clearly has skills, pace, fighting spirit and stamina but unfortunately he lacks the intelligence and vision.
He has difficulties comprehending the movement of his teammates, thus resulting with poor decision making.
I think he lacks a great support from an attacking midfielder like Ramsey so that we can only use Berna to get into simpler situations and goalscoring opportunities.
Just one-twos, runs between the lines and open shots would be sufficient. Nothing more complicated than that cause otherwise he struggles with too much responsibility.