What kind of fitness you want to practice is related to time, but it is not absolute. You should have a scientific training plan.
Even with a scientific plan, everyone's ability to accept and respond to exercise (that is, the ability to gain muscle and lose fat) is different. If someone says that it will take you as long as possible to achieve the effect in the picture, it is theoretically incorrect. But in fact, it is very possible for most boys in their twenties to reach this level through systematic training and scientific training for about one year (you don't need a personal trainer, you can surf the Internet or buy a book to study hard).