The requirement for the first 800 meters is to breathe evenly (two-part breathing, two-step breathing, two-step breathing). Endurance: Don't run too fast, just stay above the average. Endure it until the end of 800 meters, depending on your spirit. 100 meter finish, you run like crazy. Don't worry about your other problems. As for foot pain, it is normal. I suggest you strain your leg ligament before running, just moderately, but don't exercise too much!

For the record, I am also in Grade 2, 14 years old, 150 kg. . . . . . But I can finish it. Don't be afraid, just run hard.