I don't think time or km can be part of your losing pounds. Why don't you include balance diet so it will be more good result.
Is it true as your profile states you're 16? Here's the thing about running -- it's really enjoyable, you get to be outside instead of locked up in a smelly noisy gym, you get to look at flowers and trees. But every physical activity can cause injury and soreness, and everyone has a different natural ability to do that activity and so your level won't be the same necessarily as someone else. Pausing is actually quite in vogue these days and has been used by serious athletes in most sports forever -- it's called interval training these days but it has always been a way to increase endurance and strength. But that's if you do it with purpose. If you're just running for fun and activity, my own advice is to follow your body. It will tell you if you have the wind to go further or not. Every program of physical exercise comes with soreness -- if there's no soreness there's no increase in muscle and endurance -- but at some point most of us who aren't serious athletes will find a distance and a speed we like and that will be our pattern -- most of us aren't that serious about it. If you get serious about it, then that changes, and you're no longer running for fun and exercise, you're training. Training always comes with soreness. The key is to avoid injury. Soreness isn't injury. Sustained soreness that never goes away is. Most practitioners of fitness in any form will emphasize stretching, after some warm-up, to keep loose, though one person on this forum believes stretching is bad for you. Some strength training helps with anything you do. Keeping your core strong helps prevent some injuries but causes others. In other words. exercise is never without risk. Not exercising is also never without risk. People, as with all animals, need to move. The question is, how best to move. Running is one of the highest impact things you can do short of playing rugby or football. It's a lot of stress on your knees, ankles, and feet. If you're as young as you say you are, I'd think there are running groups going on at your school and you can share ideas with members of those teams. Start slowly, work you way up slowly, don't overdo it, enjoy it. But it's best if you vary your exercise so you just don't do one thing; that's a good way to try and avoid injury. But don't let injury scare you away -- life is full of injury, and as you age, it increases. Just be smart about it. Read running magazines -- they are full of interesting articles about how best to train and how to deal with and prevent injuries. But heck, if you play soccer, hitting the ball with you head causes concussions, especially in young females. There's no safe way to live, so live for pleasure and purpose and do the best you can to avoid getting hurt. And don't worry about how many km to run -- anything you do that you weren't doing before will be of benefit. Let your body tell you how many km you can run and desire to run. And try to find places where there is no pavement -- dirt paths are much softer than pavement to run on.