baby girl in nicu with Pphn

hello everyone! nicu parent here & new parent! my sweet baby girl was born a week ago at 37 weeks and a couple of days. She went about 2 hours after birth without any worries until a god sent of a nurse checked her breathing and it didn’t seem right. She ended up needing oxygen and long story short.,, she has been in nicu for a week now and we were told she has pphn. As a first time mom, I just have so many questions and I am anxious all the time. The good news is is that she is doing great and getting stronger day by day but I am still anxious about the future because i feel like there are so many steps left until she is ready to go home. Her oxygen level right now is at 23 and we are at 4 liters of oxygen and our goal is to get her down to 21 and then go to 2 liters. I am worried and anxious that she is not going to handle the liters well. I don’t have a real reason why I think that but I am just one anxious and scared momma, sometimes I just think the negative. Question: whenever y’all’s baby got 2 liters at 21% oxygen … ( with great numbers continuing ) how did he or she handle going down to 2 liters? I just have so many questions and I am just so anxious about everything and ready for my baby girl to be home with us. 💕