Three to four times a week is enough. It is necessary to give muscle time to recover, mainly because muscle cells are damaged by friction. It needs to be given time to recover the substrates (protein, fat, sugar and other energy substances, mainly protein) and digest and absorb.

20 Jin is ok, not too heavy. It's too light to squat with a barbell. You can do arm lifts, somersaults, sit-ups and the like. If you want to develop the weight of barbell and practice movements, you should make corresponding changes according to the parts you practice. Don't practice for too long every day, about 2 hours is enough. Pay attention to warm-up before practice and stretch and relax after practice, strengthen nutritional supplement, ensure adequate sleep, and pay attention to hydration before, during and after training.