Running 2.4km?

You should work up. Breathing wise, I can't answer that, when I run I have a rhythm that I don't break, just find what is right, if you're standing in line or just walking around try different breathinh techniques and see what is best for you. Start with a .5 mile. Time yourself. Then run it again for like 2 or three times. The go to a mile. Do that and just work it up. You will get there and succeed, but it will take a lot of hard work and effort, but you'll get there. Remember, if you don't put 110% into what you do, you'll never acomplish anything.