For your height and weight, your body fat rate should be relatively high. You can't practice what you want just by doing push-ups and sit-ups, but whether your abdominal muscles can be seen is a matter of body fat rate, which means that if you want to lose fat, your abdominal muscles are naturally there (they are already there, just covered with fat). If possible, I suggest you go to the gym. All kinds of barbell dumbbell training methods can be found online.