If you want to build most of your muscles in three days, I suggest you use triple differentiation training. This method divides the body into three parts: chest, back and legs. You can practice your chest and shoulders on the first day, your hips and legs on the second day and your back and arms on the third day.

Of course, this is just a method, and you can adjust it according to your own needs. However, please note that each part needs at least 48-72 hours of recovery time, so that muscles can adapt to exercise and increase strength.