my second daughter is 7month 4 weeks old and she is 7.6kg is it normal or she is under weight...at which month she will get her first teeth

A. Hello good morning !! Babies double their birth weight by 5-6 months. Check whether the baby doubled her birth weight,as per age the baby's weight is fine no need to worry. By 7-11 months babies get teeth ,yet there is time for teething. Start semi solid foods - Fruit and vegetable purie/mash,cerelac,kichdi,porridge .