You already have a good grasp of where the highlights need to be the problem is in this lighting you need more variation in colours + more shadow. You can't shy away from using a variety of 'shade amounts' as thats what shows the bumps of the face as its not a perfect sphere. Using different coloured shadows allows you to bring more depth into the the shadow itself, you can see on the reference image that some places on his skin is more pink than others. I used desaturated purples, pinks and reds in the shadows, pale yellows and brighter oranges around the highlights. Your highlights are also a little gray it looks like a more natural transition if you use paler skintones for highlights instead of going more paper white as it makes the figure look a bit ashy. Overall it's mostly about adding even more shadows so you can add a little more highlights over those areas. It might be a little easier once you learn anatomy a bit more | Artwod Feedback