It is impossible to grow pectoralis major and biceps brachii in one month, at least through normal exercise. Muscle doesn't grow for a while, it takes time, and it can't grow in a month. Besides, you are thinner and harder. But I suggest that you can do push-ups every day to complete the pectoral muscles and biceps brachii you want, and do three groups every day, 20 in each group. If you haven't done it before, you can reduce it appropriately. If you feel comfortable, you can add it slowly in the future. Pay attention to supplement protein every day and get enough sleep. You can also add pull-ups to the exercise, so that you can exercise your muscles without affecting your child's growth. Of course, the most important thing is persistence.