She said what I was going to say. You can buy some Vicks in a candle keep it burning and sinus rise in a humidifier.
We just went through this as well. Comfort care is all there is for these symptoms. Electric Nose Frida with saline spray right before was hugely helpful as well as hanging out in a steamy bathroom. It passed in about a week. Hope you both feel better soon!
Sit in the tub with your baby in a steamy bathroom If you can or sit in the shower. Try to feed the baby shortly before to promote hydration and offer a short feeding after. Keep an eye on them to make sure it’s not too hot in there but the steam was the only thing that kind of sort of helped. It’s so sad when they can’t cough things out or blow their nose. My husband also put a carefully folded towel under my daughters bassinet mattress when she was sick a few months bath to prop her head up and gently slope the rest of her body down and that helped A LOT for a cough
Currently in the same situation, baby and I are both sick. I’ve been using little remedies saline spray, a nose sucker, and hot steamy showers where we both sit and play with toys. It’s miserable.. we breastfeed and he has gotten boob round the clock. I have also given him some Pedialyte and water to help him stay hydrated.
Steam showers, suction the nose with saline spray to help loosen the mucus, cool mist humidifier and Vicks vapor rub on the feet. Unfortunately at six months old there's just not much you can give a baby to help with congestion. You might see if they have like a clinic or something you could go to to get baby section.