I got some questions about bodyweight fitness.

Can't go to the gym for 3 weeks, so I was thinking of doing 30 minutes of bodyweight daily. Is it true that in bodyweight fitness, it doesn't really matter what exercice you do, as long as you do a lot of it, or am I mistaken? Because I was thinking of doing 5 minutes of sit ups, 5 minutes of pull ups and 5 minutes of push up (whole workout 2 times) would this be a good idea, or would this work counter productive (as in overtraining). Also, I've read the faq, but most of the workouts took pretty long. Are there any effective 30min workouts that you would suggest?