Hello. My son has a fever and runny nose with phlegm flowing like a ri…

Hello. My son has a fever and runny nose with phlegm flowing like a river. I don't know if it's from his teeth or if he got sick. It's warm inside but it's also plus-temperature outside. I don't think we caught a cold. We're first-time sick people ? How can I help? I spray Aqua Maris Baby and use Snot Soother but the effect is only for an hour and then my son's nose gets stuffy again and he continues to have phlegm. I lower his temperature with Ibuprofen, paracetamol and Ceftin, alternating them. Our temperature goes up to 40 degrees. I wipe him down with a damp towel