Breastfeeding, the baby first greedily grabs the breast, eats I hear a…

Breastfeeding, the baby first greedily grabs the breast, eats I hear as it swallows within 5 minutes, starts spitting up then takes the breast again sucks like a pacifier, they say that they feed for 15-20 minutes, she doesn't eat so long, is this normal? The baby gained 1250 grams over the month.