You must have drunk too many carbonated drinks to grow your stomach and waist.
First of all, please don't drink water immediately after exercise or drink water badly during exercise. Drinking healthy carbonated drinks is a no-no.
You don't have to do sit-ups and push-ups You can do several groups of persistence every day! In your situation, you can't do too little, even if it's a group.
Upper limb strength can also do pull-ups, and then supplement it every day according to your own situation!
Practice upper limb strength with dumbbell barbells and other equipment when you have time!
Finally, the best exercise swimming is very important!