How much weight would I lose and how to increase weight loss? (in 2 weeks)?

The key is to put your plan into action. I'm working on my body too so I know. Your running and walking plan is good. To be sure, find out the correct running and walking techniques to really get fit. Try to improve your diet plan as well. You can't just eat 'a little' healthier. If you're serious about shooing that all that fat and welcoming the muscles, NO fast food. That means hamburgers, pizza, hot dogs, fries, junk food and absolutely NO SODA! Also, no high calorie food like (all kinds of) cake, cheese, etc. You can still eat white bread (because what else can we eat?) and all kinds of fruits and vegetables are encouraged. Try to do crunches as well. If you follow this, you will lose about 3lbs. But it's just a number. You will see way much less of your extra body fat and you muscles more defined. G'luck!

It takes a lot of work to burn off weight. I'm not sure how necessary it is to loose weight at 120 pounds. How tall are you? I suspect you are dangerously close to being underweight and have no need to loose weight.