For your height, you are not overweight. Assuming that your mom provides balanced meals, you can try controlling your portions sizes a bit, but since you aren't overweight, even that should not be necessary.
Since you are mostly looking for a flat stomach, I'd suggest that maybe you only need to tone your muscles, which can be done with a simple exercise routine, or even a brisk 30 minute walk each day. You can watch a lot of videos online that will help you firm up your muscles.
Try to pick up a physical activity you enjoy. Such as walking, running or swimming. Aim for roughly 30 - 60 minutes of physical activity every day. You cant spot drop. weight comes off where it wants to but if youre looking for a flat stomach you can try some ab exercises. Theres a youtube channel called diet health where they give new exercises every week. Give it a shot. Also make sure to eat three meals and three snacks a day. Also drink plenty of water. not only does it help you lose weight and prevent bloating but it makes you feel more energized. best of luck