How can I do a "simple" job on my neff1422 oven?

The problem I have is changing the oven light on my Neff 1422 oven. The instruction book says " unscrew the glass cover by turning it counter clockwise " and then change the bulb, the problem is the glass cover will not unscrew no matter how much force I use. The light is situated at the rear of the oven on the right hand side and it is not easy to get a good grip. Can someone please help ?