I have so many questions ? After feeding, I lift the baby's chair, but…

I have so many questions ? After feeding, I lift the baby's chair, but he doesn't always burp. He does it less often than not, I don't understand why ?‍♀️ All different positions have been tried, and because of that, then he goes into colic, how to fight? And how at night? Do you always raise babies for burping, I lift him, he gets fussy, then he doesn't want to fall asleep