A big, and a common, mistake that new puppy owners make is over exercising their puppy.
While puppies are balls of energy and need to run and play – they are babies and must be treated like babies. Until their growth plates have closed they should have very little or no structured exercise to protect their joints from irreparable damage. However, they should get plenty of opportunities to be outdoors and free run (that means off lead and at their own pace). See the Baqilodge Puppy Book pg. 79.
Puppy Culture: https://www.puppyculture.com/new-exercise-chart.html has a really neat exercise guidelines chart covering age groups from 8 weeks to 2 years and the type of exercise acceptable for each age group. Check it out.