Girls, hello everyone. I need advice really badly. We found out that o…

Girls, hello everyone. I need advice really badly. We found out that our baby has... in 1.5 months, LNH partial, started giving him Nutrilon lactose-free, but the pediatrician said breastfeeding shouldn't be completely excluded, the stool of the child which changes from green to dark green every day. Plus he often gets constipated and can't go potty for a long time. Should we worry? I read that changing the formula could also cause this. And how do we know if the formula is right for us?