The Nordic Hamstring Exercise (will refer to them as Nordics from now on) can be a difficult exercise to perform through full range of movement. This is the goal when performing Nordics, to get to the outer range of the movement i.e. working all the way down that the nose is touching the floor.
An exercise that can help improve the performance of Nordics is the Razor Curl, which can be seen in the videos below. Anchor ankles with the Outlier Nordic T-Bar, you then hinge (bend) through the hips and pelvis and then start to extend (straighten) the hips and knees forward allowing the hamstrings to control the movement.
The videos are in order of progression, so pick the level you are at and progress as you feel yourself getting stronger. 4/6 reps x 2 sets twice per week can be a great starting point.
Remember to cushion your knees when performing these exercises.