I have a 6 weeks old baby & she is on just breast milk. D milk does come out of her nose even after a long time of intake or belching and dis often oc
You can also keep them in the car seat put in an upright position if you are too tired or busy to carry them that long or others can help too to carry the baby.
But if it doesn't work please see your paediatrician for further management at that point.
What you just described is called gastroesophageal reflux, just a jargon that says food return from the stomach to the oesophagus after feed instead of staying down.
For such babies, you need to keep them upright for up to 30 minutes or more after each feed so it stays down.