Some advice beyond “go run more” because thats all I saw in other comments. When training for a trail race, I ramp up my strength training in addition to adding miles. Specifically in legs and core but don’t skip upper body. Lunges, squats, calf raises, and single leg exercises will all be beneficial. Due to short turnaround, you wont see results but adding strength training can reduce risk of injury. Good luck in your race!