Is this workout routine correct?

5 months ago till now I have suffered 3 strains on the hamstrings. I am now on the strengthening phase and I race in 3 weeks. I am not in very good condition for 100m but I will manage. At home when I have free time and I feel my legs are okay I perform a workout. I do it 3 times per week and target the hamstrings. The exercises I do are leg curls (swiss ball/resistance band), bridges and glute-ham raise. I start by doing 1 or 2 sets of leg curls for a warm up. Then I do 20 mins static stretching (all muscle groups) and after that I continue by doing 5 sets of 15reps of each exercise. I end the workout by doing some stretches to loosen my muscles. Am I doing the workout the right way? Or am should I change something?
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I would appreciate an answer from someone who does bodybuilding and such things or generaly knows a lot about muscle training :)
Is this workout routine correct?
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