If you can't find a suitable offline fitness class to practice abdominal muscles, I suggest you download an APP and use it to practice. The content is also very comprehensive, so you can choose your favorite exercises.

The other is to practice abdominal muscles, that is, to practice sit-ups that are often seen at ordinary times. This is slowly effective, as long as you persist, it is definitely possible.

But then again, whether you practice online, offline or at home, you should stick to it every day.