How to tone up my belly, And make it flatter?

You should do an exercise that focus on your abs only like sit ups. Running is always a good work out for you whole body especially your legs. I would suggest doing a minimum of 25 sit ups every other night. I wouldn't do it every single night because you wouldn't want your body to be sore. Create a routine and stick to it. In about 3 months yes 90 days you should see a difference. Remember nothing happens over night. What worked for ME may not work for YOU. Hope this helps.