Girls, please advise us about our underweight, can we give porridge tw…

Girls, please advise us about our underweight, can we give porridge twice a day? And how much does the child eat? Then supplement with formula? We don't drink formula very often, and can we give two times vegetable puree? Can fruits be introduced in our age? I want to make a schedule, and give a couple of tips on how to calculate everything correctly)))